Abstract: A method for roaming between cellular carriers, the method comprising: obtaining from a Home Public Land Mobile Network (home network) at least one International Mobile Subscriber Identity (IMSI) number; generating an identification code and sending it to the home network with an indication of a location of the identification code in a Packet Data Protocol (PDP) of a context request response; configuring a User Equipment (UE) with instructions to insert the identification code into a specific mandatory characteristic of the PDP, in a response to a context request received from the home network; requesting the home network to mark an UE's identification element, presenting the identification code located in the specific mandatory characteristic of the PDP, to distinguish it from other UEs; and requesting the home network carrier operator to direct incoming roaming data from the UE using a marked UE identification element to a mediating roaming service server.