Charged for goods not delivered

I received my on line order on Saturday 30th January 2016. Quite a few of the items I had ordered were missing and I had been charged for some items that had not been delivered. I made a note on the invoice, telephoned and have sent various emails. The reply I have received to my emails is that the matter is being escalated. I still have not received the refund of what I was over charged. I thought that using Pick 'n Pay on line would save me time and stress but now I am just wasting more time and getting more stressed, trying to get my refund.