A method for initiating a call in a communications system comprising a mobile communications device connected in a mobile communications network. The mobile communications device is allocated a mobile identifier for a first, mobile communications service provided by a mobile communications service provider and is allocated a second identifier for a second communications service provided by a second communications service provider that is different from the first, mobile communications service. The method comprises receiving over a data connection, at a switch, a request from the mobile communications device, comprising the second identifier, to initiate a call using the second communications service and adding, at the switch, the mobile identifier to the request and forwarding via a further network, the request comprising both the second identifier and the mobile identifier.