The present invention relates to a method and system for modifying of address information in a message routed in a packet data network, wherein the address information is changeable along a routing path of the message. In case of a change of the address information, information specifying a reason for the changed address information is added to the message, and a processing of the message is selected at a session control function based on the added information. This allows for address change operations, such as number modifications or access code additions, even in cases where an address change is generally interpreted by the session control function as a call forwarding operation.