A mobile terminal prompts a user to make a voice message upon detection of an abnormally interrupted call, and records the message. Then, the mobile terminal converts the recorded voice data and a telephone number of a communication partner's terminal into a format suitable for data communication. Next, the mobile terminal transmits the converted data to a mobile data communication relay base station. The mobile data communication relay base station forwards the converted data to a data communication network storage device via a data communication network. A stored message transmitter retrieves the telephone number of the communication partner's terminal from the data communication network storage device and calls the communication partner's terminal via a fixed telephone network. When communication is established between the stored message transmitter and the communication partner's terminal, the stored message transmitter reproduces the voice data retrieved from the data communication network storage device in response to a request from the communication partner's terminal.