PNP ASAP Charges for out of stock items

I placed an order on Pick 'n Pay ASAP a few days ago. I had to approve the order on my side when placing it but what they did not show that certain items were out of stock. Pnp then charged me for the full value of the order of R826.91 when the order was actually R299. I have called and emailed several times but they are adamant my bank must refund the money as they only charge for items thats in stock which is a LIE!!! YOU HAVE TO CONFIRM THE FULL VALUE OF THE ORDER BEFORE THAT ORDER IS EVEN CONFIRMED AT THE STORE . Even after consulting my bank I was advised that Pnp needs to process it on their side. From experience with online orders out of stock items gets credited to your wallet. This was not even done. Pnp owes me R527