A communication apparatus for supporting a registration procedure for an inbound roamer user equipment, ‘UE’, in a visited public land mobile network, ‘VPLMN’ that includes a transceiver and a controller. The controller is configured to: control the transceiver to receive, from a communicator of the VPLMN, a request for authentication information; retrieve the authentication information from a communicator of a home public land mobile network, ‘HPLMN’; and control the transceiver to transmit the authentication information to the serving CSCF of the VPLMN for use in the registration procedure.