Abstract: A method of authenticating a user's right to a mobile communication device, comprising: providing a service server comprising a database having registered service users entries, each the entries comprising an identification of the service user's mobile communication device, and an identification of the network operator used by the service user's mobile communication device; and requesting by the service server from a client application running on a first mobile communication device to send a SMS message to a client application miming on a second mobile communication device, the first and second mobile communication devices sharing the same network operator.

Abstract: A method of pushing an ongoing VVo1P call from a first currently participating communication device belonging to an account having an account ID to a second communication device, comprising: sending by the first communication device a ‘transfer call’ message to a signaling service; sending by the signaling service the ‘transfer call’ message to at least one selected second communication device; if the call is not a P2P call, sending by one of the at least one selected second communication devices a ‘connect’ message to a relay server, the message comprising authentication information; sending by the signaling service a “call transferred” message to the first communication device; and continuing the ongoing call with the selected second communication device replacing the first communication device.

Abstract: A system and method for delivering messages to participants in an instant messaging session, the participants running an IM application, comprising: receiving by a server a message from a first participant's IM application, addressed to at least one other participant; for each the at least one other participants: if the participant is active in the session—sending the message by the server to the participant; and if the participant is inactive in the session—sending a silent notification by the server to the participant.