A communications apparatus is provided. A processor is coupled to a subscriber identity card and a radio transceiver module. The subscriber identity card camps on a cell operating in a serving network having a serving network identifier via the radio transceiver module. The processor at least includes a first processor logic unit obtaining information regarding the serving network identifier, a second processor logic unit carrying the information regarding the serving network identifier in a message to be transmitted to the serving network, and a third processor logic unit transmitting the message to the serving network via the radio transceiver module.