Pick 'n Pay Online Shopping

Pick 'n Pay Online Shopping - 26 items were not delivered and the company refuses to reimburse me. The items amount to just under R500. The reason I was given was that it was my fault because I did not check every item delivered against the invoice during the delivery. I was not aware that it had now become the customer's duty to check that the order was correct. In the past, the delivery guys used to check the items. How can the customer be penalised for Pick 'n Pay's mistake? Surely this is part of their staff's duties? This is unacceptable!