I am a legal resident of Panama and entitled to purchase using a Jubilado discount when I am traveling to/from Panama. However, I use a US (UA) credit card.
Panamanian Balboas are at par with USD.
When I attempt to purchase in Panamanian Balboas using my Panamanian residency but my US (UA) card, the site automatically increases the price by a not insignificant amount. I then see it has changed my country of residency and currency in order to jack up the price, AFTER I have pushed the "buy now" button.

I believe that this is probably not legal. I should be entitled to purchase in the currency of my residency, regardless of which credit card I choose to use.
To whom do I complain, short of the US DOT or FTC? Thank you.