If you had a payment issue, please contact the support team, they are the only ones that can help you: http://support.my.com/games/kbPage/6/
(in the "name" box, explain that it's a payment issue).
Did you have an active loan? (The option which allows you to get premium crystals for "free"). If yes, it would explain the 500 missing (500=20% of 2500)
I prefer to be bad in game rather than being a trash in real life