INTERLOCUTOR

[noun] [C] [formal] - someone who is involved in a conversationIn conversation he lacks any trace of self-importance, and defers constantly to the interlocutor.(formal) An interlocutor might also be involved in a conversation on behalf of someone else.Abraham was able to act as interpreter and interlocutor for our group.The intelligence agencies were instructed to identify potential interlocutors close to the terrorists.