Switching over a voice call (DEAL 466)

This lot is generally related to telecommunications. Techniques are disclosed to switch from a voice call from an instant messaging (IM) based voice network to a cellular voice network when a user moves out of WiFi network so that the on-going call is not dropped. The system has a service network gateway with the IM-based and cellular voice networks, an IM phone agent to process IM-based voice calls from a service gateway via an IM voice network using an IM user identity, a cellular phone agent to process cellular-based voice calls using a cellular phone number and a switch-over agent. Also disclosed are techniques to send a switch-over command from the service gateway having a call reference to the switch-over agent. The technology may be implemented in IM-based networks, mobile cellular networks, mobile phones, etc.