Do you still get your receipts from the supermarket?
i got home from aldi and i felt my shopping was too expensive, i checked the receipt and there was 17 x loose red peppers = £11.90. on it and i didn't buy thoses.
simple error not a big deal but if i had not had the reciept i would never have known.
i always found it odd that they ask if you want a receipt... sketchy if you ask me.