A Web server provides the following service when being accessed by a telephone with a browser via the Internet, the server transfers a list of extension groups and the persons in charge belonging to the groups to the telephone. After the desired person in charge is selected from the list on the telephone, the server notifies the telephone of an outside-line telephone number direct-dialing-connectable to the telephone used by the person in charge. The server informs a private branch exchange of information including the telephone number of the telephone and the extension number of the extension telephone used by the person in charge. Thereafter, the private branch exchange, when receiving an incoming call from the telephone, directly calls up the extension telephone with the extension number previously notified by the server.