Exchange rate

john1966_2

I booked a room for 3 nights through a internet site, the price quoted was £105 per night,when i recieved my credit card statement i had been charged £127 when i asked why the differance they said that my credid card company would have charged a fee and that the exchange rate £s to thai bart would have made the differance.when i pointed out that my card company did not charge for this and that the price rise was all down to them and that i had checked the exchange rate and that there was only a small differance in the converted amount they then said that i was using a differant rate to them as they could be using a offshore rate , is this feasable as when i book a room at £105 i do not expect to pay £109 John1966