Account username change

So, how is it possible that i can´t change my account username? I got my account stolen, manage to retrieve it, when i came back i see that all my stuff are missing, and that ugly username. I know that with ankama would be impossible to get all my stuff back, because it was even so long since i wasn't playing that i didn't remember exactly all of it, but even if i'm pissed about, within time i can recover it, but that username doesn't have a option to be changed? I'd like a solution to this issue, if some mod could answer me this'd be terrific.

Thank you.