A communication system service billing arrangement is described that adapts to system loading in realtime. As system loading varies, one or more individual subscribers units (ISU) of a communication system are provided with realtime information on the current cost of the communication service. The system determines the locations of the ISUs and the current loading there between and calculates a calling rate based at least on the current loading. This calling rate is sent to at least one of the ISUs whose operator can choose to connect or not connect the call between the ISUs based on the current realtime variable rate.