Do it yourself. Click on personal details. Look at the bottom of the list to your left. Then hit username change.
oh sorry i didnt realize :P i just came to mineverse from a while and before they didnt let you change it yourself
You're able to change your username by yourself. Just follow this thread. If you have already changed it before, you may have to use the 'Contact Us' button on the bottom right of the page. It looks like this.