A communication apparatus is provided. A first subscriber identity card camps on a first cell belonging to a first wireless network via at least one radio transceiver module. A second subscriber identity card camps on a second cell belonging to a second wireless network via the radio transceiver module. A memory device stores a plurality of phonebook entries each comprising a destination address and information indicating one of the first and second subscriber identity cards as a preferred subscriber identity card for the destination address. A processor receives an apparatus originated communication request with a first destination address, determines the preferred subscriber identity card for the received first destination address by inspecting the phonebook entries, and establishes a wireless communication with a peer device with the received first destination address through one of the first cell and the second cells in response to the determined preferred subscriber identity card.