Years ago I had something similar happen when refunding a ticket. It was a few thousand dollars and I couldn't make it because of a sick relative. Fare rules allowed full refund for sick relative or a refund for a fee otherwise. Called to cancel before the flight and said I would send in doctor's note for full refund. AA refunded me twice--once for the amount of the fare minus fee and once for the full amount a few days later after they received my note. This caused my account to go negative by about $5000. Called back and they said everything looked fine on their end. Left my account negative assuming someone would come back asking for or just correct the refund, but it never happened. Credit card company eventually sent me a check for the balance after about a year saying I can't leave a negative balance for that long.