I had an issue like this come up when booking a hotel via entertainment.com, which links to travel.ian.com, which uses the hotels.com engine. In booking those from home it was always been fine (i.e. just the charge for the hotel stay charged on the credit card (it's always pay-in-advance, though sometimes cancellable).

Yet I did the same thing from BKK and it must've directed me to the Thai site. I easily changed the cost from baht to dollars and it was charged in dollars, but also showed up with the international transaction fee in that case. I should have tried to switch to the U.S. site.

Thankfully the mail-in rebate still worked.