They stopped name changes.
IT was an announcement if I reckon,so sorry but no name changes for you or for anyone else
I was trying to find the final thread to link you, but I can't find it, and I don't have the time to keep looking. x__x
Though, if memory serves, it happened around early 2010.
Name changes stress the server / database too much, and ideas to bring them back have been brought up, but never go through. So if you want a different username, unfortunately you'll just have to make a new account. D:
I have seen people before have their supporter status moved from one account to another. So if you wish to do so you will probably want to contact Rukario about it.