I recently ordered some items from a web site that I’d used before. The checkout price was $30, which I paid with a credit card and then forgot about it and got on with life while waiting for the items to arrive. A few days later I was checking my credit card statement, and there was the transaction, but at $31.85! Of course $1.85 isn’t worth too much effort, but it wasn’t the money, it was the principle. So I went back to the website and submitted a ticket pointing out the error. Within 30 minutes, I had a profuse apology and compensation with $10 worth of freebies - nice!