A calling party's mobile terminal includes a push-to-talk (PTT) actuator, a transceiver operable to communicate in a half-duplex mode, and a controller. SIP signaling messages sent by the calling party include information associated with one or more customized caller IDs of the calling party. The caller IDs are customized, stored, and managed by the calling party. A remote party's mobile terminal receives the SIP signaling messages, and outputs the calling party's customized caller ID to the remote party to identify the calling party.