1. A telecommunication service system for coordinating data transfer between VoIP communication terminals, the system comprising: a media server, which is a first session coordinator, configured to coordinate a VoIP session for a voice communication between a first communication terminal and one or more other communication terminal; a content share server, which is a second session coordinator, configured to coordinate a data session for a data transfer between the first and the one or more other communication terminals in response to a data transfer request from at least one of the first and the other communication terminals; a soft switch, which is a processor and which receives a first message requesting the VoIP session for the voice communication from the first communication terminal, which transmits a response message to the other communication terminals, extracts information of the first communication terminal from the message, transmits a second message to the other communication terminals, receives a response message from the other communication terminals, and sets up the VoIP session, which is performed by a session description protocol based on a session initiation protocol and transmits the voice communication in an real-time transport protocol format; and a data converter server configured to convert a data format in view of characteristics of the at least one of the first and the other communication terminals, wherein the data transfer request is received during the VoIP session, wherein the telecommunication service system determines location information of data to be shared between the first and second communication terminals and determines a sharing method which is selected from among a uni-casting method and a multi-casting method according to a contents file type, wherein the contents file type corresponds to at least one contents type from among general documents, web pages, web catalogs, characters, chat messages, image files, motion pictures, and media files, wherein coordinating the data session for the data transfer comprises using at least one from among a URI, an IP address, and a subscriber profile which used in establishing the VoIP session for the voice communication between the first and the other communication terminals, wherein the second session coordinator is separate from the first communication terminal.