exchange fees


i have a question, i tried to use my revolut card to pay a 36,44$ bill in the US.
my revolut account didnt have enougth money so the transaction was denied by revolut.
Then i used my other bank debit card to pay those 36,45$.
revolut app shows a denied transaction for 29,99€ for the 36,45$ bill.
For the same paiement, my other bank which i used the debit card shows a 29,82€ for exactly the same bill a the same time ( this bank adds after a 0,6€ fee)
So for the same transaction at the exactly same time, revolut change rate is less interresting than my « traditional » bank.
I thought revolut used the best exchange rate?
thanks for your answer