OK foods false advertising

I went to go get groceries at the Uitenhage Mosel store. P{acked in Monster which was advertised for R17.99. I asked the cashier to confirm if correct. Her immediate response was "and if it is not?" They then told me the price barcode differs from that on the tin so I won't be getting it for the price advertised. Item was on the very bottom shelf in the fridge close to the floor but they expect clients to match item barcodes with every item purchased else they won't take accountability. They falsely market products. Check your slips when supporting OK FOODS.