PURPOSE: To attain registration of addition of each extension telephone without changing immediately a setting data even if an extension number is added newly or modified by providing separatedly a call meter storing the number of calls and the setting data such as extension number to edit the number of calls servide registration.

CONSTITUTION: A call service a call meter CNT in which the number of calls is added and registered exists in a memory section 4, but no extension number is registered and the counter is in the undefined state. When a call service is calculated, whether or not the corresponding extension number is registered is checked by a control section 3 at first for the call meter CNT. Since no extension number is registered in the call meter CNT at the initial state, the corresponding extension number is registered in the counter and the call service registration calculated is stored rotally. The data inputted one after another is checked for the registration of the extension number of the meter CNT after the call service is calculated, and when the number is registered, the calculated call is added and stored rotally, and when not registered yet, the extension number is registered to the meter CNT and also the call service registration is registered together.