a message transaction method includes the steps of sending a connection request , receiving the connection request , generating a ringing response signal in response to the connection request , counting an elapsed time starting from generation of the ringing response signal , sending a disconnection request , stopping of the counting of the elapsed time upon detection of the disconnection request , comparing the elapsed time with at least one relation mapped by a lookup table , and providing a corresponding message in the matching relation . a system to implement the message transaction method is also disclosed .