It's not a dual pricing issue
[QUOTE=XXL;2962356]I saw the currency conversion screen a flash of a second but the shopkeeper was quicker. She said "of course" when I said I wanted to pay in Real and there's the result. Brazil has a dual-pricing system folks, a worse one that Thailand! The only way to avoid this would be to be the one manipulating the machine. I'm fed up with this. From now on I'll withdraw more cash from the ATM and pay everything I can I in cash. A bit of a hassle but there's no other way.[/QUOTE]You should always pay in the local currency. Paying in your currency is the scam. When you pay in your currency, they can charge you whatever exchange rate they want. In addition to that, you are typically charged a fee for that conversion. Since your bank will STILL charge you a fee for the conversion, you are not gaining anything by doing the conversion up front.
If you are charged in your local currency, you should have them cancel the purchase and redo it, ESPECIALLY if it is something expensive like a plane ticket.