Unable to log in

Hello everyone,
Yesterday (out of curiosity), just before I exited the game, I attempted to change realm to "Test Realm - IsVV2" and I got immediately disconnected. So, today I tried to log in my account and even though it connects, as soon as I log in I get disconnected and therefore I can't access my account.
How can I change the realm again without logging in my account or how do I reset the realm choice?
Yesterday (out of curiosity), just before I exited the game, I attempted to change realm to "Test Realm - IsVV2" and I got immediately disconnected. So, today I tried to log in my account and even though it connects, as soon as I log in I get disconnected and therefore I can't access my account.
How can I change the realm again without logging in my account or how do I reset the realm choice?