imsi to another when detecting an update of the elementary file comprising forbidden public land mobile networks application_number US 201013806839 A description the present invention may be understood according to the detailed description provided herein shown in fig1 is an embodiment of the method according to the invention wherein an end user uses his mobile station ms in a roaming network with the home imsi the mobile station ms has a sim card which is able to manage a home imsi and an international imsi also called roaming imsi the end user has for example moved out from india to singapore as previously described the sim card of the mobile station ms contains elementary files as specified for example in gsm11 11 such as ef loci file ef plmnsel ef fplmn u201c ef 6f7b u201d etc which are used when roaming the ef fplmn file contains a coding for forbidden plmns it is read by the ms as part of the sim initialization procedure and indicates plmns which the ms shall not automatically attempt to access thus this file only contains data on india circles of mno which means circles of mno forbidden in india a circle can be defined as a region within a country where mno operates mnc changes from circle to circle and mcc remains constant for a country the ef loci file contains data on the.