Might have paid Asset acceptance in error.

I was having a hard time with Asset Acceptance a couple of years ago. They were trying to collect on debts that may or may not have been mine and if they were mine they were extremely old. The SOL very well may have been expired but I don't know how to tell. I was pushed to take a loan out on my car in order to settle these unverified debts in exchange for a Paid in Full on my credit report and a Paid in Full letter for each. Instead I received a 1099C form for each of the 3 accounts and now have the IRS barking up my tree for back taxes. What can I do? I'm not even sure if I paid valid debts. I could have kept my $5000 and used it for my wedding. What can I do?