Bought a refundable ticket that apparently was billed into a EUR, most likely based on the country of origin, despite using a US credit card. Cancelled the ticket, and was apparently issued a refund in EUR. The original charge shows up on my CC in USD for a higher amount than the credit shows up in USD. Presumably, I lost some money based on FX rate fluctuations. Do I have any recourse with either Amex or the airline, or am I SOL?