Double payment for one meal!!!

So I went to wimpy in fordsburg on Saturday(31/08/2019) for breakfast and when paying they used one machine and said the payment didnt go through when in fact I got an SMS that it went through, they then took another machine and done another payment and it went through again. They told me the first payment will reverse and up until today nothing has been reversed. I phoned them and they said the payment is not reflecting and it shows only one payment! On my account both payments went through and I refuse to pay double for 1 meal! All I want is my money back! I dont understand why they used two different machines. I know usually it would reverse immediately when using the same machine. This is very weird and wimpy doesnt seem willing to give me my money back and help!