Had some issues with incompetent agents at SLP (wanted to use 500 mi certs for a companion, they said not possible and made us pay. Would not even downgrade to coach to issue boarding pass, but I digress).

Anyway, they charged 1020 MXN for two 500 mi certs. I gave them my card, and a few minutes later got back a receipt with DCC. Told them that I wanted to pay in Pesos, and was upset they never asked me if I wanted to pay USD. Said that I would not sign unless they fixed the issue, and they claimed it was not possible. Needless to say I had to sign to get my companion's boarding pass, but I did not tick the box. Also have picture of receipt.

Of all places, would not have expected in Mexico let alone from an AA Agent!