Credit score

Question, I had a credit card with insurance on it. I was in a car accident and I was unable to pay, that is where the insurance comes in. I've been going back and forth to court for the past 12 years because the CU should of been paying for it. Now the bank said they do not have any paperwork on my account they gave it to a collection company, which is a lawyer. I found an old form with my name on it. Thye looked at it and that was it. I feel like I should not have to pay this bill that somehow went from $4,000+ to $11,000+ and they want me to pay that. My credit is great and I do not want to file bankruptcy. Please advise what I can do.  Thank you