A method of displaying user-related information to a user on a display of a user's mobile telephony handset, the method comprising: - operatively associating the mobile telephony handset with a subscriber identification module having resident therein a file intended and used to store a service provider name of a mobile telephony network operator, the name being not differentiated for different users; - having the mobile telephone handset attach to a mobile telephony network; characterized by comprising: - detecting that the mobile telephony handset of the user is currently located in one of at least two predetermined locations corresponding to at least two mobile telephony service billing tariffs applied to the user by the mobile telephony network to mobile telephony services exploitable by the user; - in response to said detecting, having the subscriber identification module modifying a content of said file resident therein, said modifying comprising having the subscriber identification module writing in said file the user-related information to be displayed, the user-related information: - being information related to that certain user instead of being not differentiated for different users; and - being information which, when displayed on the display of the user's mobile telephony handset, is adapted to alert the user of a mobile telephony service billing tariff currently applied to the user by the mobile telephony network; - having the mobile telephony handset display on the display the content of said file. - operatively associating the mobile telephony handset with a subscriber identification module having resident therein a file intended and used to store a service provider name of a mobile telephony network operator, the name being not differentiated for different users; - having the mobile telephone handset attach to a mobile telephony network; - detecting that the mobile telephony handset of the user is currently located in one of at least two predetermined locations corresponding to at least two mobile telephony service billing tariffs applied to the user by the mobile telephony network to mobile telephony services exploitable by the user; - in response to said detecting, having the subscriber identification module modifying a content of said file resident therein, said modifying comprising having the subscriber identification module writing in said file the user-related information to be displayed, the user-related information: - being information related to that certain user instead of being not differentiated for different users; and - being information which, when displayed on the display of the user's mobile telephony handset, is adapted to alert the user of a mobile telephony service billing tariff currently applied to the user by the mobile telephony network; - being information related to that certain user instead of being not differentiated for different users; and - being information which, when displayed on the display of the user's mobile telephony handset, is adapted to alert the user of a mobile telephony service billing tariff currently applied to the user by the mobile telephony network; - having the mobile telephony handset display on the display the content of said file.