Charged double for 1 transaction and never refunded

I'm extremely annoyed with Pep stores right now. On the 25th April I went to Pep Hatfield to pay off my lay bye. I paid with my FNB card and then I was told that the transaction is hanging and won't continue but R723.79 was already deducted from my card. I was then told that they're going to scan the items yet again and another R723.79 was taken from my card when they scanned it again. The amount was never reversed back to my FNB account and that has caused a HUGE inconvenience for me as I need my money RIGHT NOW! How the hell do you charge a person for one transaction twice PEP??? R723. 79 is a whole lot of money which I would kindly appreciate if you can refund it back to me ASAP! I really can't be inconvenienced because of your system error and then get told to wait!? And I've heard that always happens to most people when they use their FNB card at Pep. Please sort out your messed up system because you've caused me a huge financial inconvenience as customer as that money was for paying something else. I want my money back Pep and I want it NOW!