When you use your Whipapp card to place transactions in foreign currencies, Visa’s exchange rates will be applied to the full purchase amount.
Whipapp charge 0.75% extra fees for foreign transactions.
You can check Visa’s rates here: https://www.visa.co.uk/support/consumer/travel-support/exchange-rate-calculator.html
Please be aware that exchange rates are dynamic, so the transaction value can change until the final purchase amount is charged due to currency variation.