Before you make any exchange or foreign transaction on the Revolut digital service, the fees you will be charged will be shown on the screen. If you are not okay with the cost, you can decide not to continue with the transaction. In that way, you will not have to pay the fees.
Nonetheless, the smartest way to avoid paying Revolut fees is to upgrade your account to Revolut Premium or Revolut Metal. For example, for a fee of 6.99 GBP per month, Revolut Premium removes the limits and fees on your foreign exchange, gives you up to 5% cashback on your expenses, allows you to make free international money transfers, and lets you withdraw up to 400 GBP for free every month.