I took out a cash advance and paid it off early, but they cashed my check of a paid off loan?

everything went good, I signed the loan payoff paper and got my check back. A day or two later the manager called me and told me that they had messed up and I had gotten the wrong check and if I could bring it back. I told her that I shredded it, I usually do that with my checks since they have my signature and personal information. I later found out that I got my ex-girlfriend's check, we shared a checking account, but we haven't been together for almost a month now and I told check-n-go to call her because it was her debt and not mine. they left me alone for the past two weeks until I looked into my checking account and saw a charge for $229.45, My ex won't call me back and the main offices at check-n-go were useless. What I'm wondering is if I could take legal action towards check-n-go for charging my check for a paid off loan? if there is, where should I start?