The invention relates to a fee management server (6) for managing subscriber fees. Said fee management server (6) manages an actual fee credit TG and an available fee credit VG for every subscriber. Upon receipt of a fee accounting message by a servers (ACS) for accounting fees for a communication service desired by the subscriber, the fee management server (6) transmits a recall message for recalling communication units already allocated for another communication service if the available fee credit TG of the subscriber is lower and if an actual fee credit TG is higher than an amount specified in the fee accounting message for the desired communication service.