A data transmission method for transmitting data from a first communication device to a second communication device, a data transmission system and a communication device can be provided. An identification message associated with the data is sent from the first communication device to the second communication device via a first cellular network. The data is transmitted from the first communication device via a first medium, other than the first cellular network, coupled to a server of a service provider of the cellular network, for transmission of the data to the second communication device.