Checkers n1 city robbing customers by overcharging

Me and my wife shop at checkers N1 city every week even twice a week as its very close to home. They keep overcharging us on products. The last time we had 3 products being overcharged. This keeps on happening. We go to the customer care to get our money back, we fill in the form and after we receive our money nothing happens. They don't rectify their prices for the next customer. The overcharging is deliberate and this is unacceptable. They are robbing you blind. I think its time that we boycote the shop.