I had a very similar situation. Refund went to a US credit card that had been closed for over 6 months and (as I learned later) had been returned to BA very promptly. It ended up in a suspended account at BA which I think is a holding place for orphaned funds. To resolve it took persistence. I did a lot of it through the chat feature, and sometimes by phone. In short, I had to get the date BA sent the refund to my credit card, the exact amount and ARN number. That has to be supplied by BA. I gave that to my credit card issuer who gave me the same information regarding the return to BA. In my case the ARN was the same as the one BA gave me, the amount was obviously the same, but the date was different. BA were then able to locate the funds in a suspended account and refunded them to me on a different open credit card which ironically is what I originally asked them to do. It took several attempts on chat to get someone to escalate the issue to the Accounting department who provided the ARN, and even then I had to follow up several times before getting the data. Upon receipt of the return information from the credit card issuer, I had to start again to get the accounting department involved. Once that was done it went reasonably fast. Someone from the accounting department eventually got in touch, found the funds and refunded them. You cannot call the accounting department directly, they will call you. All in, it took about 3 months and a lot of persistence. That was half way through Covid, so possibly faster now? Perhaps asking your credit card issuer to inform you of the return ARN, date and amount would speed things up because once BA had those three pieces of information things moved quite quickly. Anyway, hope this helps. Recommend you use chat over the phone because there is a record you can see, and you can take screen shots.