Telecommunications method, and system suitable therefor, for establishing a connection with a mobile device, for example a GSM mobile radio telephone, of a participant, who is located in a VPLMN, the calling mobile participant in the VPLMN preparing and sending a short message, for example a USSD message, with the desired destination number, which will be passed on to a callback computer, which establishes a connection between the calling mobile participant and the desired destination number, and a connection being established with a called mobile participant in a VPLMN by a callback computer, whose number is assigned to this called mobile participant in the home location register.Before the establishment of a connection, checking, in a prepaid module connected to the callback computer, the remaining credit and the remaining airtime of the mobile participant with reference to stored prepaid amounts, or respectively with the aid of at least one tariff table and on the basis of an indication of location of this participant stored in the HLR of the HPLMN.