Contacting a store after paying less for an item due to an error in their system
Q: I paid less than I should have when I went to the supermarket a few months ago due to an error in their checkout system. I messaged their customer service online on the day and they said “Thank you for your honesty. There's nothing much we can do about it at here at Customer Services but if you do wish to get rid of the difference you can return to the store and speak with the Customer Service desk.”
Am I sinful if I don’t go back and return the difference? I’m not 100% sure if I still have the receipt.