we had a similiar thing happen to us twice.

While on international travel, tickets were purchased on my partner's AS Mastercard for tickets on SWA for various trips within TX.

Both times, charges were disputed, the trips had been flown, but Bank of America credited her account.

She now has blocked SWA on her card.

Sounds like you use your amex alot, I guess you wouldn't want to do that.

good luck.
lala