Misleading of customers at Clicks Gordon's Bay

We experienced on numerous occasions that Clicks Gordon's Bay (maybe in other areas too) advertise items on promotion at a certain price but charge the normal higher price. They usually give the money back but it is conspicuous that it happens so often and never in the favour of the customer. 5 days ago I bought 2 tubes Sensodyne (buy 2 at R60). At home I realized that they charged me the normal price for a double pack of R68. This time I unfortunately didn't get my money back as they must have moved the ad on the shelve. The manager told me that I have to show them proof that there was an ad on the shelve. I asked her if I shall have a look in her shop to find this special ad? She surely knew that there was a promotion maybe by mistake on the shelve which they must have taken off in the meantime. This is misleading and cheating of customers and it happens all the time and nobody stops them.