From FAQ
"How can I change the information in my profile?
It is your responsibility to keep the information in your profile up-to-date. You should especially ensure that your email address is kept current. You can alter any of the fields in your profile, except your username. Once you have registered your username, it becomes yours for life. In extreme circumstances, you may request that the administrator change your username, but he or she will require a very good reason to do so."