Abstract: There is provided a method of a modification of a message in a communication system and a device for execution of the method. After receiving a message, the message being delivered into a receiver communication unit through data communication means and stored in a storage unit, there is a password allocated to the sender, the password being allocated with respect to available information about an identity of the sender, and the password is delivered back to the transmitter communication unit as acknowledgement message and serves the sender as a key for obtaining an access to functions of modification and/or deleting a message stored in the receiver communication unit.