A mobile device identifies multiple, different networks available to a client resident on the mobile device, and sends multiple registration messages to an outbound proxy over the multiple, different networks via first, second and third communication interfaces. The mobile device determines whether access has been lost to a first network of the multiple different networks, and sends an invite message via the second communication interface, based on the determination, for an outbound call via a second network of the multiple, different networks for routing the outbound call via the second network.