Abstract: An apparatus for verifying service user's information consists of a switch system for setting a call between one terminal and the other terminal and a data memory connected to this switch system. This data memory stores information indicating the number of a service user on which a charge previously applied by a subscriber is imposed and information on a validity of this service user's information. The switch system includes a checking section. The checking section checks at first effects, when the subscriber requests setting of a call to be charged for a talk on the basis of the above-mentioned information from one terminal, a formal check of the service user's information sent with the request by the subscriber. If this formal check is passed, the checking section requests the data memory for a collation as to whether or not the service user's information is valid.