A communication system including a communication system, including a modular cell phone, including a baseband modem for connecting to a core mobile network via a cellular network, and a connector for physically connecting the modular cell phone to a port of a mobile electronic device, and a mobile electronic device, including a modem for connecting to the core mobile network via an IP access network, a port for physically connecting the modular cell phone to the mobile electronic device, and a connection enhancer for receiving a connection of an ongoing cellular phone call, between the modular cell phone and the core mobile network via the cellular network, and seamlessly handing over the ongoing phone call to a voice over IP connection, between the mobile electronic device and the core mobile network via the IP access network, in response to the modular cell phone being connected with the mobile electronic device port. A method is also described and claimed.