The character Xiaoyizi on the pvp server has never been banned. You (or someone else) may have attempted to log in too many times with an incorrect password. Wait 30 minutes to an hour and try again. If you can't remember your password you can reset it at https://en.nostalrius.org/password
Perhaps the country IP lock is causing it. Please try changing your password and changing the IP lock that might be on the account either so that it points to your country, or is deactivated. Let us know in this thread if it doesn't solve the issue.