If I'm not wrong, you could contact staff and they could arrange something. There actually has been pat ideas that suggested username changing, however I've never really thought it would be good to have a username changing device. It would be too confusing having lots of people going all like 'Oh I'm so and so, remember?'. There's a small group of people who had their usernames changed it's very confusing when you do encounter one, this group would get larger if we did have an item.