My bank account was levied (frozen) by Forester & Garbus but the debt amount looks wrong, what to do?

I received a notice that a levy/lien was placed on my bank account and that I should contact Forster & Garbus. According to the bank, the collection agency received a court judgment which allows them to put a levy on my account. There are 2 things I am unclear about: 1. The amount they claim I owe is double the amount that I remember seeing on my last bill for that debt, can they add charges and inflate the amount I need to pay?
2. At the time when they received the judgment against me I was not in the country, so I had no way to respond. Does that make a difference?
Once a judgment has been made and a levy placed on my bank account do I have any option but to pay that absurd amount?
Any help will be greatly appreciated.