Provided are a system and method for network transitions. In one example, the method includes receiving messages from a mobile device indicating that the mobile device is in a session initiation protocol (SIP) wireless hotspot and that the mobile device is engaged in a communication session via a cellular network while in the SIP wireless hotspot. The cellular network is instructed to add the mobile device to the communication session via the SIP wireless hotspot. An affirmative response is received from the cellular network and a third message is sent to the mobile device to notify the mobile device of the affirmative response.