Yes, You are going to have to contact an admin to change your user.well, first i don't think you can even change your username anymore. there'll be an announcement in-game when you can, until then you're gonna have to wait, or make a new account if the name "Viana" isn't taken.
secondly, if there was a username change event going on, you'd have to contact an admin by inbox privately instead of posting it publicly on a forum.