Abstract: A mobile transaction system comprising: a user's mobile phone, a mobile network of any provider, a transaction device equipped with a microphone, a transaction processing center with dynamic early media generation capability and with the capability of communicating with the mobile network, wherein, upon a mobile phone user's call through the mobile network to the transaction processing center, the transaction processing center detects the call and, instead of answering the call, starts transmitting user identification data as a dynamically modulated signal through an early media connection to the mobile network and further to the user's mobile phone; wherein, the speaker of the user's mobile phone reproduces the modulated signal, which is then captured by the transaction device through the microphone.