Abstract: A method for use when a mobile communication device roams between a home network and foreign networks, which device includes a SIM card using an IMSI, includes the steps of storing on the SIM card a first IMSI for network identification; upon receipt of a location update message indicating that the mobile device has moved to a first visited network, firstly causing the HLR to send an instruction message to the mobile device to change, to a second IMSI, the IMSI used for network identification; secondly causing the mobile device to use the second IMSI for network identification and saving the first IMSI; and then causing the mobile device to perform a device network refresh; and upon roaming back to the home network, causing the mobile device to change the IMSI used for network identification back to the first IMSI and then to update its network status.