Abstract: A communication system includes a call answering center; a first mobile phone that registers a call answering setting in the call answering center; a second mobile phone that makes a call to the first mobile phone and includes a display unit and an operation unit; and a telephone communication network that connects the first mobile phone, the second mobile phone, and the call answering center in a communicable manner. When a call is made and the call answering setting is performed, the call answering center composes a call answering message accompanied by a reply program having an advertisement image attached thereto in accordance with the call answering setting, and transmits the call answering message to the second mobile phone. Upon receiving the call answering message, the second mobile phone causes the display unit to display an image of the reply program having the advertisement image superimposed thereon.