PNP Online error

I placed an online order with Pnp and their online system is not very user friendly so what happened was I selected the incorrect options and ended up receiving my order twice which I lodged a complaint with them immediately when I got the second order which I did not order. I made my first call and the guy who helped me rushed the call first and then call me back only to rush the call again not giving me an opportunity to explain what my problem was. He made a promise the first day that my money will be paid back and refunded to my bank account. Two weeks later I followed up as He said the refund will take 48/72 hours which never happened. I made four calls to PNP for one mistake made and ended up with a bank charged of R300 taken off my account for their mistake and system. I was lenient with them saying that I received a duplicated order which was short-supp**** but my account was debited for the full amount of the invoice include delivery fees. I followed up again after receiving a PAY U REF from them and the guy promising again that all incorrect funds will be refunded include my bank charges for the mistake by PNP. I only received an email yesterday after my 4th call to Pick N Pay and is currently on email with the escalations person who has now come back to tell me that the bank charges are for my own account and that they will not pay me back for it even if this was not my mistake. What am I now to do in this case and up to today no refund has been done to my account at all. Who is able to guide me in getting all my money back from PNP.