I've had a lot of different scenarios play out in the last couple of weeks, and someone hit the nail on the head earlier by suggesting that you go to the top of the food chain.
Your first job should be to contact them and make sure you're escalated to the VP or Prez or CFO someone with absolute authority. Then you should explain the situation to them entirely -- all of this should be accomplished in a peaceful manner. If you are able to do this I can almost certainly guarantee you that your case will be closed, the additional fees dropped or reduced and your credit cleared.
Any other approach is drawn out and will not get you the ultimate results you're looking for.
Let us know how it gets resolved
I'm quite curious.