FEP Blue claim denied 1 month after approval

Not sure if this question belongs here or in r/legaladvice.

My wife and I have Blue Cross Basic federal insurance based in WV. My wife had a few therapy sessions with a provider in Maryland. Since the provider does not do their own insurance billing, back in June I submitted a claim form via the secure message. We kept getting letters saying that they were still working on the claim for months. Finally, at the beginning of last month, we received a response stating that the claims were processed and a refund check to go with it (My wife previously paid for therapy in full). The check covered several sessions and we were happy with it. We cashed the check, it went through, that was the end of it. However, about a week ago we get a letter in mail, saying that the claim was not supposed to be paid and to give BCBS a call back. After several hours on the phone with them, they indicated that the claim was paid by Blue Cross in WV and they should not have issued a payment. This should have been sent to BlueCross in MD. They stated that they will send out a letter demanding repayment. I get it that someone critically messed up and this was an error. However, I feel like there should be some rules or laws against insurance companies re-claiming issued checks after they were issued and cashed. Other than paying the money back and re-submitting the claim to MD, do we have any other options?