A technology is disclosed for providing an additional function control system which permits a carrier to select whether or not an additional function possessed by a communications terminal can be made available. A communications network is connected to a communications terminal when using a communications function of the communications terminal which is subscribed to a communication service. An additional function controller manages the additional function of the communications terminal, and provides the communications terminal with additional function control information for controlling the operation of the additional function. The communications terminal comprises an additional function unit for providing the additional function, and limits the operation of the additional function unit based on the additional function control information from the additional function controller.