I will admit this predicament is a little embarrassing but I have to know. I printed out papers front and back and when the cashier asked how many papers, I told her but I never mentioned it was front and back. I genuinely thought they charged per paper and not per printing (so one paper printed front and back would've charged me twice of that which was printed only front). At the time, I didn't know that and I only payed probably half of what should've been the price (mind you, it's actually more than half because they always give discounts but at most, it's half).

Should I go back and give them the rest of the money? It would be very embarrassing to be honest and now, I obviously pay as should, so should I just keep going to them for papers/supplies so I can give them my money rather than going to their neighboring competition?

Please no one judge me too harshly, I was genuinely oblivious.