False advertising on products

Yesterday I went to Pick n Pay Witpoortjie to get a couple of things. I saw that the OXY was on special. Buy 3 and get the cheapest free. Which I did. I brought a face wash, cleaners, moisturizer and a small OXY blitz tube. When we paid I saw on the slip that the cheapest item wasn't free. I asked the cashier which called the supervisor. She took everything from me and come back to me more then 5 minutes later. She took out the specials pamphlet and told me you have to buy the soap then you get the soap for free. I told her didn't see the pamphlet but then the sign they put up was worded wrong then. I told her this is false advertising as nothing mentions that you have to buy the soap and the soap is the only thing for free. After about 20 min she refunded me on the one product which was the cheapest. I got home and looked at the pamphlet and on there, also nothing is mentioned that only the soap is free. How can Pick n Pay put up a special and not adhere to the special. This means they are *****ing from their clients. How many more people have brought the OXY products knowing that they were suppose to get the cheapest product (any of the products) for free and didn't. Not everyone checks their slips as they are in a hurry. According to me this means, their system is also not programmed right. How many of the other specials are there that you think you are getting but then you are paying normal price because the system hasn't been programmed for that special.