A method performed by stations to transfer call sessions between different access networks. The methods include transmitting, by a first station to a second station, an invite to join a voice call on a first radio access network (RAN), receiving, by the second station, the invite, generating, by the second station, a response to the invite, determining, by the second station, that the response cannot be successfully transmitted to the first station, associating, by the second station, with a second RAN, generating, by the second station, a message indicating the second station has associated with the second RAN, transmitting, by the second station, the message to the first station, retransmitting, by the first station, the invite to join the voice call, receiving, by the second station, the invite on the second RAN and setting up the voice call between the first station and the second station.