Method and system for transmitting useful data between telecommunication devices

The invention relates to a telecommunication device (10,18) is for transferring service data method and system, the prepay access data comprises a first digital key and control data, stores a telecommunication device (10) memory module (11), a digital key storing in a communication network (14) one or multiple control unit (16) is. The valid received by according to the control data, further in long and valid received consistent; and coding the first telecommunication device service data the first key. The service data transmission of the code to the control unit (16), decodes a second digital key and transmitted to the telecommunication device (18).