I’ve tried BNL (BNP) atms in France, they don’t charge anything extra.
Are you sure you didn’t let the ATM do the conversion? You need to either “Decline” it, or choose a “Standard” withdrawal… the wording depends on ATMs.
Take a look at this message, there is a picture from a BNP (=BNL) atm: 5% ATM Fees in the First withdrawing within my country !