Overcharge and bad service

Pick n pay Lakeside has on several occasions overcharged me on items. They also sometimes advertise two different prices for the same product. Today I was overcharged on two items. Only very small amounts but they make a lot of extra money by overcharging on small amounts that people don't bother to query. So I pointed out the one overcharge when I paid, as I want them to fix it. The second overcharge I pointed out later in the day, after I noticed it on my slip. They had advertised two different prices on one product. The difference being R2. I hadn't asked for a refund I was just trying to show them it's confusing for the shopper having different prices. The manager just said she doesn't know, banged down R2 on the counter and walked off. No apology or explanation, I'm sorry to say I think it was quite rude behaviour. I was being quite polite. Surely as manager (or assistant manager, I'm not sure), she could have apologised for the confusion and politely asked if I would like a refund? Every day consumers are ********** and when we politely point out something wrong with a price we get treated very badly. I think we have the right to speak up and I think we have a duty to speak up. We live in a world where honesty has gone down the toilet and it's all about money. Well not in my book. Shops have a duty to charge the correct price. I also advise shops if I have been undercharged which sometimes happens. We must be honest and fair. I would ask that pick n pay trains it's managers on how to correctly feel with customer queries. Thank you.