Double the Difference dispute

I bought Panados which were marked on the shelve as R18.99. When I got to the till, it scanned as R20.99. I informed them that this has scanned incorrectly and I should get double the difference. They refused and instead contacted the supervisor (Crystal) to come over. This process took a good couple of minutes while the the line grew longer. When Crystal arrived I politely explained that I should get double the difference but she debated with me as to why I can only get that double the difference if i already paid the incorrect price. She then corrected the price on the till so that I ended up paying R18.99<br> <br> I don't understand the logic to this because I could have simply kept quiet, paid and then reported the issue to the supervisor to get double the difference. Surely the policy is that if it scans differently, and not if you pay differently? <br> <br> What happens to the other customers who have walked out of pick n pay unaware that they have been overcharged. Surely the management must take responsibility for this negligence. I have been left disappointed in Pick n Pay after this episode. <br> <br> I look forward to your response.