We usually do not change user names. Actually, we never change user names because we can't do that. There is a procedure that comes close. You create a new account and an admin can merge the old account into the new account. But as a rule, we do not do this unless the user has a lengthy record of contribution (usually defined as 150 posts or more).

But I'm willing to make an exception for you. If you want to proceed, create a new account with the desired name and then send me a PM.