There is a new "facility" you may encounter when paying by credit card in a
foreign currency. The POS terminal identifies which country your credit card is
from and conveniently converts the local currency into your home currency. Your
credit card is then billed in your home currency rather than the local currency.

Might sound helpful, but the catch is that the exchange rate at which the
conversion is done is almost certainly a lot worse than your bank would use if
you got billed in the local currency. The retailer usually gets a cut of the
exchange rate markup so it's in their interest to bill you in your home
currency.

They are supposed to ask you which currency you want to billed in, but it
practice it doesn't always happen, and the default is to bill you in your home
currency. But you are perfectly entitled to insist you are billed in the local
currency, after all the product or service will have been priced in the local
currency. Don't let retailers rip you off in this way!

--
Andy