if you were cheating on it.. then you cant really get it back... but if you were wrongfully frozen.. then you can fill out a form in the contact us section on neopets. if that still doesnt work i think there is a guide on how to use the better business bureau to unfreeze your account.
Nice. I'd never thought of using the BBB before, LOL. Those guys... I like what they try to do, but I feel like they often get used as a pawn too. As for the frozen account, good luck. If you really were cheating, chances are you really won't get your account back. But it's always worth a shot.
Neopets are very set in stone when it comes to trying to get back accounts. Instead of giving you access again, they refuse, get you to make another so you keep bloating their user count -_-