A data transmission method and apparatus for performing a data transmission between end terminals of a telecommunication network, where the data is transmitted from at least one of the end terminals using the first data bearer. Then, data transmission is switched from the first to the second data bearer, if a predetermined bearer need condition has been determined or in order to obtain a subscriber identity used for gathering charging data. The network service provided by the operator can be improved, since the bearer switching allows an increase of the overall speed of the data transmission, an adaptation of the bearer bandwidth to the data amount, and a provision of the subscriber identity. The first data bearer may be a USSD or SMS data bearer, and the second data bearer may be a circuit-switched data bearer or a GPRS bearer, or vice versa.