Do I need to pay?

Hi. Was wondering if anyone has been in a similar situation and has any advice on a ‘fine’ I received.

I received a letter through my door the other day to say that I drove off from a service station without paying. When I checked, the amount of fuel i’d ‘drove off’ with was £53.

I wouldn’t dream of driving off without paying, i’m not struggling financially and im no thief.

I then checked my bank and I had a charge on the same day and time noted in the letter for £5.30. Obviously the cashier has entered £5.30 instead of £53 and as I just tapped my phone with apple pay not thinking, I hadn’t realised.

I’m more than happy to pay the outstanding amount it’s clearly just a mistake, but the debt company who sent me a letter out of nowhere have added a £40 fee on top and I really want to fight this out of principle.

I can afford to pay, but i’m honestly so pissed off that I’ve never been given an opportunity to right the wrong and they’ve slapped a fee of 80% on top of the original amount!

Why on earth do they get to take £40 from me for absolutely no reason, the station should surely have some accountability for entering the wrong amount.