A communications system and method of transferring data over the communications system. The system includes audio communications devices (telephones and/or, soft phones) connected to Session Initiation Protocol (SIP) endpoints with multiple line capabilities and a unique Uniform Resource Identifier (URI) associated with audio communications that has the form x@y.z. A file transfer agent system running a File Transfer Application Agent (FTAA) application is also connected at each of SIP endpoints, and has a unique URI that has the form ft.x@y.z. Parties conducting a phone conversation at SIP endpoints can initiate file transfers between the file transfer agent system from respective audio communications devices without otherwise accessing the file transfer agent system.