In Denmark, we've had a special national card since the 1980s, called 'Dankort'. The fee for any transaction is 0.50 DKK, regardless of the transaction's size. This means that Dankort is almost
always cheaper to use than Visa or Mastercard.
As such, almost every store in Denmark accepts Dankort. But - like every other place - they are not allowed to pass that charge onto consumers directly. So it mostly happens indirectly, i.e. the prices in the stores. It is important to note, that until a few years ago, there was no transaction fee on Dankort transactions. It was practically a public subsidised credit card system.
And it worked great.
Now the EU is requiring that bundled cards get a choice. You see, one disadvantage of the Dankort was that it only worked in Denmark. So they made a deal with Visa to make a bundled card, called 'Visa/Dankort'. In Denmark, it would use the Dankort part and abroad it would use the Visa part.
But now consumers are required to make a choice for each transaction whether they want to use the Visa or Dankort part. It might seem great that you get a choice, but there is really no reason to pick the Visa part in Denmark. But since stores aren't allowed to pass the costs directly onto the consumers who pick Visa, prices are likely to go up, even if just 1% of every transaction is suddenly a Visa transaction.
I assume these rules are part of the capping of fees in the rest of the EU, and many Danish observers also suggest that these rules probably work great in the rest of the EU, just not that beneficial in Denmark.