the price on shelf and paid price not the same

We bought a colourinbook and the price on the shelf was R16.99. At the till we pay R32.99. The owner was not willing to give it for the R16.99 price but only for R25.00 althoug I insist on paying R16.99. He is just saying that the barcodes doesn't corresponce and that he doesn't have to give it to me for that price because their policy say so. I feel that when I go every month to buy my R4000 - R5000 groceries I do not have time to check every items barcode to the price tag on the shelf because I as the customer expect it to be right as to that is why they have employees who earn a salary to make sure this is right. It is not my job to stand and verify barcodes. I would have understand if this was with only one book but the whole batch where on the same place under the R16.99 price. Its not like I want a fridge for the books price, it was all just colouring books. Simi**** products. I feel PicknPay need to get this right because I do not go around in places and check barcodes.