Charged double for their online glitch

On Saturday, 3 December, we stopped at Wimpy Vaal East 1 Stop for breakfast. When we paid the transaction went through (bank SMS confirmation received) but the supervisor / manager told us it would be reversed and forced us to pay despite showing him the SMS confirmation that the transaction went through. Said they normally experience problems with online transactions when there's load shedding. We were then made to repay, we then paid with another card, it also went through. We have been waiting for an amount of R533.20 to be reversed, it has not, it's been 6 days now. When we try to call the number we were given, it goes straight to voicemail.