Fee for forced faktura?

I crossed the Øresund bridge a few weeks ago when their systems were down. Usually I've paid on the spot with a card, but didn't have the option that day. Today I recieved the bill at my Norwegian address. There's a 40kr faktura fee - can they charge this when they gave no other option but to pay via faktura because of their system failure?

When I ask this, what I mean is, sure, they can put the extra fee on the paper because it's probably standard, but can I just ignore it, pay the amount of the normal bridge toll, and then say I'm not legally required to pay an extra fee when it's the company's fault they couldn't take my payment on the spot in either cash or card? Also, I had no way of knowing this until I was at the toll both where you can't turn around, so it's not as though I "agreed" to pay via faktura beforehand.

I know It's a small thing, but I'm seriously considering sending it to Forbrukerrådet or some other government agency. There is a "small fee creep" happening in a lot of Scandinavian companies, and I'm getting tired of it and am ready to push back if this is the right place to do so.