A communications server for routing communications traffic between a first communications apparatus and a second communications apparatus, the second communications apparatus comprising at least a first mobile subscriber identity and a second mobile subscriber identity, the first mobile subscriber identity being associated with a first network operator in a first geographic region and the second mobile subscriber identity being associated with a second network operator in a different second geographic region, the server comprising: a list of all mobile subscriber identities of the second communication apparatus; input means arranged to receive a communications signal from the second communications apparatus informing the server that the second mobile subscriber identity is active on the second communications apparatus and that the other mobile subscriber identities of the second communication apparatus are inactive, the communications signal received via the second network operator associated with the second mobile subscriber identity; input means arranged to receive communications traffic from the first communications apparatus directed to one of the inactive mobile subscriber identities of the second communications apparatus, the communications traffic received via the first network operator associated with the inactive mobile subscriber identity; processing means arranged to determine the active mobile subscriber identity of the second communications apparatus based on the list of mobile subscriber identities and based on the communications signal received from the second communications apparatus; and output means arranged to route the communications traffic intended for the inactive mobile subscriber identity of the second communications apparatus to the active mobile subscriber identity of the second communication apparatus, the communications traffic routed via the second network operator. a list of all mobile subscriber identities of the second communication apparatus; input means arranged to receive a communications signal from the second communications apparatus informing the server that the second mobile subscriber identity is active on the second communications apparatus and that the other mobile subscriber identities of the second communication apparatus are inactive, the communications signal received via the second network operator associated with the second mobile subscriber identity; input means arranged to receive communications traffic from the first communications apparatus directed to one of the inactive mobile subscriber identities of the second communications apparatus, the communications traffic received via the first network operator associated with the inactive mobile subscriber identity; processing means arranged to determine the active mobile subscriber identity of the second communications apparatus based on the list of mobile subscriber identities and based on the communications signal received from the second communications apparatus; and output means arranged to route the communications traffic intended for the inactive mobile subscriber identity of the second communications apparatus to the active mobile subscriber identity of the second communication apparatus, the communications traffic routed via the second network operator.