Lifeatyle centre called me a criminal

I recently went to the lifestyle centre as I regularly purchase from them. I took a a water pump that had a price diaplayed R109 on. As They scanned it at the till they acknowledged the actual price was almost a R1000 higher. The cashier proceeded to remove the price originally displayed of the box, called the manager and when I calmly explained it was not my mistake the manager told me I probably changed the price myself and it was not their problem it was wrong. I am a very good customer of them and I am not looking for free items but the way they handled me was utterly disgusting and being made out as a criminal was really unfair. Do not shop at this centre.