Double charged on credit card -no assistance

I shopped at Mr Price Sandton City and their systems went down. I was charged on my credit card and then the staff insisted I pay cash again as the transaction had not cleared. The staff then signed acknowledging that I was charged cash and paid on the credit card.I have been phoning and calling all week. I have spoken to Sibongile, and khetiwe. Each time they promise to assist and no one gets back or takes calls. Worst of all NO ONE even answers calls. What kind of a retailer is this! I have proven over and over that I was indeed charged. Eventually when I spoke to Bev I was asked for my info all over again. This is MY MONEY and I want it back. As I write this I have been promised that this matter will be resolved once again