Abstract: A service system for providing a service to a user comprises an application accept unit (4) for accepting an application for registration from a terminal (1) together with a telephone number of the terminal, a recording module (5) for recording the telephone number as an application telephone number, a telephone call receiving unit (6) for receiving a telephone call, a comparing unit (6) for comparing a caller telephone number of the received telephone call with the application telephone number, and a registration module (5) for registering, when the caller telephone number is coincident with the application telephone number, the application telephone number as a registered telephone number.