Misleading prices

Hi, as I often buy products from a specific store of Carrefour Market, in rue du Marche aux Poulets 40-52, I noticed that the prices on the shelves are not those that are charged at the cashier, misleading the buyers and overcharging them. I complaint twice to the staff about this, but I see that this malpractice continues. For example 2 days ago, I bought an iceberg for 1,49/per piece while on the shelf the price was 1,29 / per piece. And many more examples. Also, in many products there are no prices at all. I once asked the manager, how am I supposed to know the price and his answer was I should know it beforehand and check every price on the cashier!!!!