You can use your card regardless of the currency of the country you are in, as long as Visa payments are accepted by the merchant and the POS in which you are using your card.
Please note that the exchange rate is calculated by Visa and your account will be charged according to the exchange rate on the date of the transaction clearance and not on the date the transaction took place.
If you are expecting a refund from another currency, be aware that the amount refunded may differ from the amount of the original payment. This is because the exchange rate will be recalculated at the moment the merchant's bank issues the refund.
You can check the fee charged by Magenta Pay in our price list.