You may have to set up a new account. There was an exercise a few months ago whereby name changes could be requested but that exercise has been completed (and some members didn't get their changes). As far as I know it was one-off as I can't remember it happening before and I got the impression it caused the Ed and techies a few headaches
Ed says in Username Amnesty further down this list that one of the things not to be used is real names. That's where I read it and decided I had to change mine.