The invention relates to a telecommunications method which enables a visited mobile radio telephone network (VPLMN, VPLMN') to be connected to a subscriber of a home mobile telephone network (HPLMN) without roaming agreements with the home mobile radio telephone network (HPLMN). To this end, a first IMSI number (IMSI1) from a number range of the subscriber's home mobile telephone network (HPLMN) and a second IMSI number (IMSI2) from the number range of a partner network (PPLMN) are assigned to the subscriber. The partner network (PPLMN) can be used via additional roaming agreements, and a common subscriber's number (MSISDN) is assigned to both aforementioned IMSI numbers (IMSI1, IMSI2). Both IMSI numbers (IMSI1, IMSI2) can preferably be stored on a common identification module or on different identification modules.