KR20090015755A - Apparatus and method for changing call mode for prepaid subscriber - Google Patents

Abstract

A call mode conversion method of a user who subscribes a prepaid service and an apparatus thereof converting an image call into a voice call in a user terminal of the prepaid service are provided to maintain a long conversation time by converting the image call into the voice call. A receiving mobile terminal(110) is connected to an image call through mobile radio communications network(S300-S304). The balance information request signal requesting the balance information of the caller terminal(100) in which the image call is connected is transmitted to the CDR server(S306). The balance information corresponding to the balance information request signal is received from the CDR server(S310). It is compared with the designation balance in which the balance information is stored within the caller terminal(S312). The voice call change over report signal is transmitted with the recipient's mobile station and the voice call change over answer signal is received from the recipient's mobile station(S312-S322).

Description

Apparatus and method for changing call mode for prepaid subscriber}

The present invention relates to a method and apparatus for switching a call mode, and more particularly, to a method and apparatus for switching a call mode in a user terminal subscribed to a prepaid fee service.

Recently, the penetration rate of mobile phones has increased rapidly, and mobile phones have become a necessity for modern people. Such a mobile phone can be referred to as a functional multimedia communication device because it provides not only a voice call service but also various data transmission services and various additional services. A prepaid fee service is provided as a kind of such supplementary service, and recently, a video call that allows a user to talk while looking at the other party's face is also provided.

The prepaid fee service is a service that saves a fee for using a mobile phone by prepaying a certain amount in advance in order to control the fee of a mobile phone.

In the case of a user subscribed to such a prepaid fee service, the usage fee is limited, and there is an inconvenience in that a call cannot be continued if the balance of the prepaid fee is exhausted even during a call. In addition, since a video call is more expensive to use than a voice call, it is necessary to convert the video call to a voice call before the user of the user who subscribes to the prepaid fee service runs out. Therefore, it is required to change the call mode by allowing the user who is in the video call to know the current balance.

The present invention provides a method and apparatus for switching a call mode of a user subscribed to a prepaid fee service, which is devised by the above-described needs.

That is, the present invention checks whether the caller terminal subscribed to the prepaid rate service connected to the receiver terminal and the video call has the remaining balance up to the present, and if it is less than the designated balance, the method of switching the call mode of the user subscribed to the prepaid rate service to switch to the voice call And an apparatus.

Technical problems presented by the present invention will be easily understood through the following description.

According to an aspect of the present invention, a call mode switching method is provided.

According to an embodiment of the present invention, a method for switching a call mode by a caller terminal subscribed to a prepaid rate service, the method comprising: connecting a video call with a receiver terminal through a mobile communication network; Transmitting a balance information request signal for requesting current balance information of the caller terminal to which the video call is connected to a charging server; Receiving balance information corresponding to the balance information request signal from the charging server; Comparing the balance information with a designated balance stored in the caller terminal; And transmitting a voice call transfer notification signal to the receiver terminal and receiving a voice call transfer response signal from the receiver terminal when the balance information is less than or equal to the designated balance. There is provided a call mode switching method, wherein the video call is converted into an audio call.

The method may further include displaying information on the current balance on an information output unit of the caller terminal, when the balance information is less than or equal to the designated balance.

In addition, if the balance information is less than the specified balance, the call mode further comprises the step of indicating whether or not to switch the voice call to the information output unit of the caller terminal and maintains a video call or switch to a voice call according to the selection of the caller terminal A conversion method is provided.

If the balance information is less than or equal to the designated balance, indicating whether to switch to postpay payment in the information output unit of the caller terminal, and maintaining prepaid payment or switching to postpay payment according to the selection of the caller terminal. Provided is a call mode switching method comprising.

In addition, when switching to postpaid payment according to the selection of the calling party terminal, indicating whether the voice call is switched to the information output unit of the calling party terminal and maintaining a video call or switching to a voice call according to the selection of the calling party terminal. Provided is a call mode switching method comprising.

In addition, when switching to postpaid payment according to the selection of the caller terminal, the billing server is provided with a call mode switching method characterized in that to settle the fee after the deducting of the prepaid fee.

In addition, when the balance information is less than or equal to the designated balance, the receiver terminal receives the voice call transfer notification and displays voice call transfer information indicating that the voice call is switched to the information output unit of the receiver terminal. A method is provided.

In addition, the information output unit is provided a call mode switching method, characterized in that the display or speaker of the terminal.

In addition, the balance information received from the billing server is a balance information calculated after the billing server receives the balance information request signal, after calculating the fee used by the caller terminal to date from the prepaid fee is provided by the call mode switching method do.

In addition, the specified balance is provided a call mode switching method, characterized in that the predetermined amount of money set in advance by the user in the caller terminal subscribed to the prepaid rate service.

In addition, the specified balance is provided a call mode switching method, characterized in that the preset amount in proportion to the prepaid rate of the caller terminal subscribed to the prepaid rate service.

According to an embodiment of the present invention, a method for switching a call mode by a caller terminal subscribed to a prepaid fee service, the method comprising: receiving a video call request signal for requesting a video call connection; Transmitting a balance information request signal for requesting current balance information of the caller terminal receiving the video call request signal to a charging server; Receiving balance information corresponding to the balance information request signal from the charging server; Comparing the balance information with a designated balance stored in the caller terminal; And when the balance information is less than or equal to the designated balance, the video call request signal is converted into a voice call request signal, and a voice call is sent to a called party terminal.

According to an aspect of the present invention, a mobile communication terminal capable of switching a call mode is provided.

According to an embodiment of the present invention, in a mobile communication terminal connected to a charging server through a mobile communication network, a balance information request signal including current balance information is generated and transmitted to the charging server, and the balance information request signal A transceiver for receiving corresponding balance information; A balance processing unit which compares whether the balance information is a predetermined designated balance; When the balance information is less than or equal to the designated balance, a mobile communication terminal including a call processing unit for transmitting a voice call transfer notification message to a receiver terminal and receiving the voice call transfer response message to connect a voice call is provided.

In addition, when the balance information is less than or equal to the specified balance, a mobile communication terminal is provided further comprising an information output unit for outputting at least one or more of whether the current balance, whether the voice call is switched, and whether the postpay bill transfer.

In addition, when the balance information is less than or equal to the specified balance, a mobile communication terminal is provided which indicates whether to switch the voice call and maintains a video call or switches to a voice call according to the selection of the caller terminal.

In addition, when the balance information is less than or equal to the specified balance, a mobile communication terminal is provided which indicates whether to switch to postpaid payment and maintains prepaid payment or switches to postpaid payment according to the selection of the caller terminal.

In addition, when switching to postpaid payment according to the selection of the calling party terminal, a mobile communication terminal is provided which indicates whether to switch the voice call and maintains a video call or switches to a voice call according to the selection of the calling party terminal.

In addition, when the balance information is less than or equal to the designated balance, the receiver terminal receives a voice call transfer notification and displays voice call transfer information indicating that the call is converted to a voice call.

In addition, the balance information, the billing server receives the balance information request signal, calculates the frequency calculated by the caller terminal subscribed to the prepaid rate service to date, and calculates the remaining balance of the caller terminal to the present A mobile communication terminal is provided which is calculated information.

In addition, the balance processing unit is provided with a mobile communication terminal, characterized in that for storing a predetermined balance which is a predetermined predetermined amount.

Through the method and apparatus for switching the call mode of the user subscribed to the prepaid fee service according to the present invention, it is possible to continuously monitor whether or not the balance of the caller subscribed to the prepaid fee service is exhausted.

In addition, it is possible to maintain a long talk time by converting the voice call to a relatively low-cost voice call before the balance is exhausted through automated processing for maintaining the call.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

In addition, in the description with reference to the accompanying drawings, the same components regardless of reference numerals will be given the same reference numerals and duplicate description thereof will be omitted. In the following description of the present invention, if it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic structural diagram of a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 1, a mobile communication system 100 according to an embodiment of the present invention includes a caller terminal 100, a receiver terminal 110, and a billing server 120 connected to them through a mobile communication network 130. can do.

Here, the caller terminal 100 and the receiver terminal 110 may be applied without limitation as long as the user terminal capable of a video call, the caller terminal 100 may be a terminal subscribed to the prepaid fee service. In addition, the billing server 120 is connected to the caller terminal 100 and the receiver terminal 110 through the mobile communication network 130, receives a balance information request signal from the caller terminal 100, the caller who is using a prepaid fee The balance information of the terminal 100 may be calculated to transmit corresponding balance information.

That is, the caller terminal 100 connected to the video call through the receiver terminal 110 and the mobile communication network 130 may communicate with the charging server 120 and receive the current balance information. In addition, the caller terminal 100 may receive the balance information from the billing server 120, and if the balance is less than or equal to the preset balance, the caller terminal 100 may switch to a voice call during a video call with the receiver terminal 110. Hereinafter, the operation of each component of the mobile communication system 100 according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 5.

2 is a block diagram of a caller terminal according to an embodiment of the present invention.

Referring to FIG. 2, the caller terminal 100 according to the present invention may include a transceiver 200, a balance processor 202, and a call processor 204, and may further include an information output unit 206. In addition, the caller terminal 100 is connected to the charging server 120 through the mobile communication network.

The transceiver 200 is connected to a mobile communication network and is in charge of various signal processing in the terminal. The transceiver 200 generates a balance information request signal for requesting balance information of the caller terminal 100 subscribed to the prepaid fee service, and transmits the generated balance information request signal to the billing server 120. In addition, the transceiver 200 receives the balance information corresponding to the balance information request signal from the charging server 120 and transmits the balance information to the balance processing unit 202.

The balance processing unit 202 receives the balance information received from the billing server 120 and compares the designated balance stored in the caller terminal 100 to determine whether at least one of a voice call transfer and a postpaid payment transfer are made. .

The call processing unit 204 is responsible for various call processing related to call connection. In detail, the call processor 204 determines a call type (video call or voice call) input from the caller terminal 100 and transmits the call to the receiver terminal 110. In the present invention, if the input call type is a video call, the call processing unit 204 may interwork with the billing server and continuously receive balance information of the caller terminal to determine whether to switch to the voice call.

The information output unit 206 may be a display screen, a speaker, or the like provided in the caller terminal 100, and outputs various types of information. For example, whether the current balance, voice call transfer, post-payment transfer can be output. The format output from the information output unit 206 may be displayed as text information on the display screen, display a specified tone or voice message, or may be output in the form of vibration of the terminal.

3 is a flowchart illustrating a method of switching a call mode of a user subscribed to a prepaid fee service according to an embodiment of the present invention.

Hereinafter, a call mode switching method in the caller terminal 100 subscribed to the prepaid fee service according to an embodiment of the present invention will be described in detail with reference to FIG. 3.

The caller terminal 100 transmits a video call to the receiver terminal 110 through the mobile communication network 130 (S200). The receiver terminal 110 receives a video call sent from the caller terminal 100 through the mobile communication network 130 (S202), and the video through the mobile communication network 130 between the caller terminal 100 and the receiver terminal 110. The call is connected (S304).

Here, the caller terminal 100 may be a terminal of a user subscribed to a prepaid fee service in which a predetermined fee is paid in advance. Therefore, when the prepaid fee is exhausted, the mobile communication service cannot be provided. Therefore, the caller terminal 100 may set a predetermined amount in advance, and if the balance is less than or equal to the remaining amount, the caller terminal 100 may be notified of the balance and convert the video call into a voice call.

The caller terminal 100 to which the video call is connected sends a balance information request signal for requesting the current balance information to the charging server 120 connected to the mobile communication network 130 (S306).

The billing server 120 receives a balance information request signal from the caller terminal 100 and generates balance information of the corresponding terminal (S308). The balance information refers to the amount of the balance of the usage fee to the present time from the usage fee prepaid by the caller terminal 100.

The billing server 120 transmits the generated balance information to the caller terminal 100 (S310).

The caller terminal 100 receives the balance information so far from the charging server 120 and checks whether the received balance information is the designated balance (S312).

Here, the designated balance is a criterion for determining whether to switch the call mode to a preset amount in the caller terminal 100 subscribed to the prepaid fee service. The designated balance may be set collectively in proportion to the amount prepaid to the prepaid rate service, or may be arbitrarily set by the user in the caller terminal 100. In addition, the designated balance may be arbitrarily changed in the caller terminal 100.

If the balance information received from the billing server 120 is less than or equal to the specified balance, the caller terminal 100 displays whether the balance is currently present in the caller terminal 100 and receives a voice call transfer request (S314). Here, the caller terminal 100 may attempt to switch to the voice call immediately after receiving the voice balance request without displaying the current balance.

The caller terminal 100 receiving the voice call transfer request transmits a voice call transfer notification message to the receiver terminal 110 through the mobile communication network 130 (S216). The voice call transfer notification message notifies that the video call being connected is converted to the voice call and includes a signal for connecting the voice call.

The receiver terminal 110 receives a voice call switch notification message including a signal for connecting a voice call (S218). The receiver terminal 110 receiving the voice call transfer notification message transmits a voice call transfer response message to the caller terminal 100 (S320). When the caller terminal 100 receives the voice call transfer response message (S322), a voice call is connected between the caller terminal 100 and the receiver terminal 110 through the mobile communication network 130 (S324).

Thus, the caller terminal 100 connected to the video call can maintain a long talk time by switching to a voice call before the balance is exhausted.

4 to 6 are flowcharts illustrating a method of switching a call mode in a caller terminal to which a video call is connected according to an embodiment of the present invention.

Each step to be described below may be steps performed in each component included in the caller terminal 100 according to an embodiment of the present invention, but is performed in the caller terminal 100 for the convenience of understanding and explanation. Collectively. Therefore, the subject performing the steps to be described below can be omitted as the caller terminal 100.

Referring to Figure 3, the video call is connected between the caller terminal 100 and the receiver terminal 110 (S400).

The caller terminal 100 to which the video call is connected receives the balance information from the charging server 120 connected to the mobile communication network 130, and checks whether the current balance is present (S402).

The caller terminal 100 determines whether the current balance of the caller terminal 100 is less than or equal to the designated balance (S404), and if the specified balance is not reached, sends a request signal to the billing server 120 for balance information, The balance information is received to receive balance information corresponding to the request signal to continuously check whether the current balance.

Here, when the balance information is received from the charging server 120, the caller terminal 100 may periodically send a request signal for the balance information, and receive the balance information corresponding to the request signal for the balance information. In another embodiment, the billing server 120 may periodically transmit balance information to the user terminal subscribed to the prepaid fee service.

On the other hand, when the current balance of the caller terminal 100 is less than or equal to the specified balance, the caller terminal 100 outputs a balance notification display indicating the current balance (S406), and switches to a voice call (S408).

Here, the balance notification display may be variously displayed through text, a signal tone, a voice message, a vibration, and the like through the information output unit 206 provided in the caller terminal 100.

In addition, a message indicating that the call is switched to a voice call according to whether or not the caller terminal 100 is exhausted may be transmitted to the receiver terminal 110 which is the counterpart terminal.

Referring to FIG. 5 as another embodiment of the present invention, steps S400 to S404 described in FIG. 4 are performed in the same manner.

Then, when the current balance of the caller terminal 100 is less than or equal to the specified balance, the caller terminal 100 displays whether or not to switch to a voice call (S500).

Here, the indication of whether the voice call is switched may be variously displayed through text, a signal tone, a voice message, a vibration, and the like through the information output unit 206 provided in the caller terminal 100. The user may determine whether to switch the voice call displayed on the caller terminal 100 through a selection button of the terminal. Here, the selection button may be a numeric button existing in the terminal, or may be a call mode switching button provided separately, and the matter regarding input of the selection button may be included together in the voice call conversion indication information.

When the user does not input the selection button or whether the user inputs the selection button for maintaining the video call, the video call is maintained until the current balance is exhausted (S502).

On the other hand, when the caller terminal 100 inputs a selection button for switching to the voice call with respect to whether or not the voice call is switched (S504). In this case, a message indicating that the call is switched to the voice call according to whether or not the caller terminal 100 is exhausted may be transmitted to the receiver terminal 110 which is the counterpart terminal.

Referring to FIG. 6 as another embodiment of the present invention, steps S400 to S404 described in FIG. 4 are performed in the same manner.

Thereafter, when the current balance of the caller terminal 100 is less than or equal to the designated balance, the caller terminal 100 displays whether to switch to postpay payment (S600).

Here, whether to switch to the postpaid payment may be variously displayed through text, a signal tone, a voice message, a vibration, and the like through the information output unit 206 provided in the caller terminal 100. The user may determine whether to switch to the postpaid payment displayed on the caller terminal 100 through the selection button of the terminal.

When the user does not input the selection button or inputs the selection button for maintaining the prepaid payment, whether the user switches to the postpaid payment or not, the user selects whether to switch to the voice call and converts the video call to the voice call (S602). . In this case, a message indicating that the call is switched to the voice call according to whether or not the caller terminal 100 is exhausted may be transmitted to the receiver terminal 110 which is the counterpart terminal.

When the user inputs a selection button for switching to postpaid payment, whether or not to switch to postpaid payment, the user is selected whether or not to switch to a voice call and is switched to a voice call (S602), or maintains a video call (S612).

 In the case of switching to the postpaid payment, the user subscribed to the prepaid rate service can be converted to the postpaid rate from the time after the prepaid call rate is used up, thereby maintaining the communication service.

In the above, the method of switching the call mode by the caller terminal 100 while the video call is connected between the caller terminal 100 and the receiver terminal 110 has been described. ) And the video call is not connected between the receiver terminal 110 and the receiver terminal 110. Hereinafter, the differences will be mainly described in FIG. 7.

7 is a flowchart illustrating a method of switching a call mode in a caller terminal that has sent a video call according to an embodiment of the present invention.

The caller terminal 100 receives a video call request signal for requesting a video call connection from the user (S700). The video call request signal may be generated when the user clicks a specific button for making a video call. In the following description, the caller terminal 100 receives an image call request signal generated by a user click. However, this embodiment may include a case where the current balance is confirmed after the video call request signal is transmitted from the caller terminal 100 to the mobile communication network.

The caller terminal 100 receiving the video call request signal receives balance information from the charging server 120 connected to the mobile communication network 130 and checks whether the current balance is present (S702).

The caller terminal 100 determines whether the current balance of the caller terminal 100 is less than or equal to the designated balance (S704), and if the specified balance is not reached, sends the video call to the receiver terminal 110 (S706).

On the other hand, if the current balance of the caller terminal 100 is less than the specified balance, the caller terminal 100 outputs an indication for converting the outgoing video call to a voice call (S708), and transmits a voice call (S710).

Although the above has been described with reference to embodiments of the present invention, those skilled in the art may variously modify the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. And can be changed.

1 is a schematic structural diagram of a mobile communication system according to an embodiment of the present invention;

2 is a block diagram of a caller terminal according to an embodiment of the present invention.

3 is a flowchart illustrating a method for switching a call mode of a user subscribed to a prepaid fee service according to an embodiment of the present invention.

4 is a flowchart illustrating a method of switching a call mode in a caller terminal to which a video call is connected according to an embodiment of the present invention.

5 is a flowchart illustrating a method for switching a call mode in a caller terminal to which a video call is connected according to another embodiment of the present invention.

6 is a flowchart illustrating a method of switching a call mode in a caller terminal to which a video call is connected according to another embodiment of the present invention.

7 is a flowchart illustrating a method for switching a call mode in a caller terminal that has sent a video call according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

100: caller terminal

110: receiver terminal

120: billing server

130: mobile network

Claims (20)

In the method of the caller terminal subscribed to the prepaid rate service to switch the call mode, Connecting a video call with a receiver terminal through a mobile communication network; Transmitting a balance information request signal for requesting current balance information of the caller terminal to which the video call is connected to a charging server; Receiving balance information corresponding to the balance information request signal from the charging server; Comparing the balance information with a designated balance stored in the caller terminal; And If the balance information is less than or equal to the designated balance, transmitting a voice call transfer notification signal to the receiver terminal and receiving a voice call transfer response signal from the receiver terminal, And when the voice call transfer response signal is received, the video call is converted into a voice call. The method of claim 1, When the balance information is less than or equal to the designated balance, And displaying information on a current balance on an information output unit of the caller terminal. The method of claim 1, When the balance information is less than or equal to the designated balance, And displaying whether or not the voice call is switched to the information output unit of the caller terminal and maintaining a video call or switching to a voice call according to the selection of the caller terminal. The method of claim 1, When the balance information is less than or equal to the designated balance, And displaying whether to switch to postpay payment in the information output unit of the caller terminal, and maintaining a prepaid payment or switching to postpay payment according to the selection of the caller terminal. The method of claim 4, wherein When switching to postpay according to the selection of the calling party terminal, And displaying whether or not the voice call is switched to the information output unit of the caller terminal and maintaining a video call or switching to a voice call according to the selection of the caller terminal. The method of claim 5, When switching to postpay according to the selection of the calling party terminal, The billing server is a method of switching the call mode, characterized in that after the end of the fixed amount of the prepaid charges to settle the charges. The method of claim 1, When the balance information is less than or equal to the designated balance, And the receiver terminal receives the voice call transfer notification and displays voice call transfer information indicating that the voice call is switched to the information output unit of the receiver terminal. The method according to any one of claims 2 to 7, And the information output unit is a display or a speaker of a terminal. The method of claim 1, Balance information received from the billing server is Receiving the balance information request signal by the charging server, and calculating balance after calculating the fee used so far by the caller terminal in the prepaid fee. The method of claim 1, The designated balance Call mode switching method characterized in that the caller terminal subscribed to the prepaid rate service is a predetermined amount set by the user. The method of claim 1, The designated balance And a preset amount in proportion to a prepaid fee of a caller terminal subscribed to the prepaid fee service. In the method of the caller terminal subscribed to the prepaid rate service to switch the call mode, Receiving a video call request signal for requesting video call connection; Transmitting a balance information request signal for requesting current balance information of the caller terminal receiving the video call request signal to a charging server; Receiving balance information corresponding to the balance information request signal from the charging server; Comparing the balance information with a designated balance stored in the caller terminal; And And when the remaining balance information is less than or equal to the designated balance, converting the video call request signal into a voice call request signal and sending a voice call to a receiver terminal. A mobile communication terminal connected to a charging server through a mobile communication network, A transceiver for generating a balance information request signal including current balance information and transmitting the balance information request signal to the billing server and receiving balance information corresponding to the balance information request signal; A balance processing unit which compares whether the balance information is a predetermined designated balance; And a call processing unit for transmitting a voice call transfer notification message to a receiver terminal and receiving the voice call transfer response message when the remaining balance information is less than or equal to the designated balance. The method of claim 13, When the balance information is less than or equal to the designated balance, And an information output unit for outputting at least one of a current balance, voice call transfer, and postpaid payment transfer. The method of claim 13, When the balance information is less than or equal to the designated balance, A mobile communication terminal which displays whether or not a voice call is switched and maintains a video call or switches to a voice call according to a selection of a caller terminal. The method of claim 13, When the balance information is less than or equal to the designated balance, A mobile communication terminal indicating whether to switch to postpaid payment and maintaining prepaid payment or switching to postpaid payment according to a selection of a caller terminal. The method of claim 13, When switching to postpay according to the selection of the calling party terminal, A mobile communication terminal which displays whether or not a voice call is switched and maintains a video call or switches to a voice call according to a selection of a caller terminal. The method of claim 13, When the balance information is less than or equal to the designated balance, And the receiver terminal receives the voice call transfer notification, and displays voice call transfer information indicating that the receiver terminal is switched to the voice call. The method of claim 13, The balance information The billing server receives the balance information request signal, calculates the frequency calculated by the caller terminal subscribed to the prepaid fee service to date, and calculates the balance of the caller terminal up to the present; Characterized in a mobile communication terminal. The method of claim 13, And the balance processor is configured to store a designated balance which is a predetermined amount of money.

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