Double transaction

On the 22 September 2017 I went to Nandos Bloemfontein Westdene at 9:20 as I wanted to get their special I waited there for them to open. I went in to buy the food when they opened at 10:.03:12 transaction was done and was successful as I received a notification from the bank The lady struggled to get the slip on the till then she said it shows that it went through she is just awaiting for slip to come out After 3 minutes the slip was still not out and the other lady was busy assisting her they said I should swipe again. I showed them the message on the phone they said other customers just swipe without complaining as the money will be reversed during the day. My question to them was what if I have only R180 in my bank as we are in the middle of the month am I not going to get the food even when I showed them the message on the phone the lady who was assisting me nodded her head. In life we are not equal other customers they swipe from the abundance they have the money in my bank account was only R400. I was going to pour petrol with the remaining as I'm getting paid on the 26 What an awful experience I had to swipe again at 10:07:34 the second transaction was done and it deducted the money again meaning in total I paid R360 for R180 meals. I'm still awaiting for my money to come back. If I did not have money I was not going to get the food and I was going to feel ashamed to walk out in empty hands and the store was full of people including my colleagues