To allow a speech party to select a charging system offering a comparatively low cost among a plurality of charging systems in a speech utilizing a telephone network.

When a caller terminal 13a and a called terminal 13b start a speech, a voice reproduction section 5 reproduces advertising information as voice information and transmits the information to a caller exchange 9a. The voice reproduction section 5 stops reproduction and output when the speech is finished. A sound volume V of the voice information is adjusted in response to number of push tones from the terminal 13a. The sound volume V is set in total 10 stages from 0 to 0.9 at an interval of 0.1. The volume V is decreased by 0.1 each every time one push tone is outputted through the operation of a key '1' from the terminal 13a. The volume V is increased by 0.1 each every time one push tone is outputted through the operation of a key '3' from the terminal 13a. A charging calculation section 1 calculates a call frequency to calculate charging on the terminal 13a on the basis of inter-exchange distance information from an exchange control network 11, speech time information from a timer 3, the volume V of voice information from the reproduction section 5, and a prescribed formula.