Items incorrectley billed with NO refund

On Black Friday this year I purchased 10 buckets of 10KG HTH Chlorine from Pick and Pay online. The items cost was indicated at R239 per bucket. After delivery, I realised that I was charged R339 per bucket. I do recognise that I actually paid the money and the fault is somewhat mine. The above numbers are easy to transpose. I certainly expect that the online system compiling the order would be able to do math correctly. The same day of the delivery, (four days later) I called the help line to find out what could be done. The answer was that the difference would be refunded. 5 calls and 21 days later, I still have no refund. The only answer I get is that the online department is not responding. Can someone at P&P PLEASE do something about this dismal service?