A method of transmitting data, the method being performed by an apparatus for transmitting data, comprising the steps of: receiving a request for a call signal, from a sender device to a receiver device, including sender and receiver information associated with the call signal from the sender device; receiving address information associated with the sender, in which content associated with the sender is stored, from the sender device; confirming a relationship, between the sender and the receiver, that exists in at least one server, based on the received sender and receiver information; identifying whether content is stored in association with an account of the sender; if content is identified to be stored in association with the account of the sender, selecting the stored content and transmitting the call signal together with the selected content to the receiver device; and if content is not identified to be stored in association with the account of the sender: requesting, from at least one external server to which the sender is subscribed, content associated with the sender which is most recently uploaded based on the received address information associated with the sender; receiving the requested content from the at least one external server; selecting the received content associated with the sender; storing the selected content associated with the sender in association with the account of the sender; and transmitting the call signal together with the selected content to the receiver device. receiving a request for a call signal, from a sender device to a receiver device, including sender and receiver information associated with the call signal from the sender device; receiving address information associated with the sender, in which content associated with the sender is stored, from the sender device; confirming a relationship, between the sender and the receiver, that exists in at least one server, based on the received sender and receiver information; identifying whether content is stored in association with an account of the sender; if content is identified to be stored in association with the account of the sender, selecting the stored content and transmitting the call signal together with the selected content to the receiver device; and if content is not identified to be stored in association with the account of the sender: requesting, from at least one external server to which the sender is subscribed, content associated with the sender which is most recently uploaded based on the received address information associated with the sender; receiving the requested content from the at least one external server; selecting the received content associated with the sender; storing the selected content associated with the sender in association with the account of the sender; and transmitting the call signal together with the selected content to the receiver device. requesting, from at least one external server to which the sender is subscribed, content associated with the sender which is most recently uploaded based on the received address information associated with the sender; receiving the requested content from the at least one external server; selecting the received content associated with the sender; storing the selected content associated with the sender in association with the account of the sender; and transmitting the call signal together with the selected content to the receiver device.