PnP robbing us

I placed an order 30 Nov. There was meat in my order and because PNP charge the highest amount when ordering meat I ended up having a credit of R632 in my wallet. I then ordered 10 Dec using my credit, but my order was cancelled and my credit dissapeared. I contacted PnP numerous times. Everyone is very apologetic and promising. After many calls I received a promo code for the R632 and was happy that my problem has been resolved. I then placed an order 19 December which totalled to R1107,90 excl delivery fee and driver tip. I ordered Meat again. I used the R632 and paid R530,90 with my card. The meat totalled to R853,94 in my cart and I received meat to the value of R571,06. My wallet or my account was never credited with the difference. I'm not sure who developed PnP's invoices, but it really sucks. I called the call centre and send many emails but they keep on telling me that I have been charged less for my order. I mean why the Hell would PnP charge me less on everything in my order. Seriously I even asked them to calculate the order I had in my cart but they also failing to do that The invoice the call centre sent me only shows the amount that I paid with my card and not the R632. It dissapeared in thin air. So everything on there has been discounted to the total paid with my card. I really don't know how to explain this to them anymore. I really need help regarding this. What's worse is that I have to explain over and over, I'm really tired now. I have even sent pictures of everything but no one seem to understand. I'm not sure if that is how we are been rob. I have never had problems B4 and enjoyed ordering from PnP. But lately it's as if they are really trying to rob me.