A second communication mode can be enabled for a source device and a destination device. Each device can be a mobile device having a first communication mode and a default number for the first communication mode. The default numbers for the source device and the destination device can be stored. A call request can be received from the source device operating in the second communication mode. The call request can be directed to the default number of the destination device. The destination device can be determined as a client based on the default number of the destination device. A communication session can be established between the source device and the destination device over a network upon determining the destination device is an active client.