Disclosed are techniques for hosting a communication session in a call server between communication devices. The call server functions as a bridge service between the communication devices joining an original communication link between the first communication device and the call server with a second communication link between the second communication device and the call server. The first communication device includes at least two RF transceivers each capable of communicating with the call server over a separate network using separate telephone numbers. The call server establishes an alternate communication link with the first communication device on an alternate network and joins it with the second communication link before disabling the original communication link to maintain the communication session between the communication devices.