Overcharged R50 on a R180 bill

I was at Sunningdale Pnp I had 2 Errors of overcharging. 1 was for spinach and the other for peanut butter. I picked up 3 peanut butters which were on promo, however , when I happened to check the bill, I was charged R26 instead of R19.99. I thought they would refund the entire price of 19.99 on each of those peanut butters and spinach, thats what Pnp Sea Point did for us if there is a price error. And thats also what Woolworths does. Anyway, so the customer service told me that is no more a policy, we will pay back double the difference which was R10 on each. So the manager told me, he was happy to pay double the difference on the 3 peanut butters but not on spinach, because the barcode did not match the tag at the display. We obviously dont shop seeing the barcodes and thats not our problem. That was the limit, where we told him we dont want the pay back , we want a refund, (R50 total) and left the store as he kept debating about his policy without making the customer feel that they were apologetic for 2 major price errors on technically 4 items. And This was not the first time Pnp had overcharged. They should really make up for such errors