Currency switches back to default currency when paying.

Hi, Currency Switcher works on the front end and it even changes the currency to desired one while on checkout, the currency amount remains the same as the changed one but the currency itself reverts back to the default currency. I’ve KWD as the default currency and let’s say I’ve got a product costing 20 KWD and I change the currency to USD the new amount will be $65.3 USD and it shows it just like that, but now if I go to checkout and pay amount will remain “65.3” but currency goes back to KWD which means customers are paying triple the actual amount of the price of the product. Please help.