Users (1) may communicate with each other by means of so-called “chat” services (6) via internet (4). Chatting users often prefer to remain anonymus, while using “avatars”, nicknames etc. There may be a need to change, at a certain moment, from data-oriented to e.g. voice-oriented chatting, without losing the users' anonymity. After having agreed -via the data-chat service (6)- on an ID code, the users may initiate a new, voice based chat domain via a voice network viz. by entering the agreed ID code into a voice-chat service (7). That service matches the received ID codes and establishes a new, voice based chat session between users entering matching ID codes.