Disclosed is method comprising: storing in a home location register (HLR) at least one subscription record of a mobile device of the plurality of mobile devices, the mobile device having a subscriber identity module (SIM) identified by a currently activated first international mobile subscriber identity (IMSI), the currently activated first IMSI belonging to a set of IMSIs allocated to the system, wherein the provisioning server is operative to: receive a notification that the mobile devices has moved into a first one of the wireless networks; confirm that an allocation rule is satisfied; add and activate a second one of the IMSIs in the set of IMSIs to the HLR and remove the currently activated first IMSI from the HLR; and send the second IMSI to the mobile device to enable the mobile device to communicate wirelessly in the first wireless network as a local device.