Your Genome card is a EUR currency card. This means the transactions will be processed in EUR by default.
If you have additional accounts in GBP or USD, you would be able to pay in these currencies without the additional conversion rate, if the balance in those currencies is sufficient for the particular card transaction. Otherwise, when paying by card in any other currency, the amount of the transaction will be converted from EUR to the other currency and the additional FX rate will be applied for this transaction.
Before paying in another currency, please make sure, that "Conversion to EUR" is enabled in your card settings. What is more, the FX rate on transactions in other currencies is 2%. You can find more information about the FX rate in this Article.