Unnecessary Customer humiliation

I went to Mountain River Spur in Thavhani Mall on sunday 24 July 2022 with my family. When the bill came it was R1518. I paid R1800 including tip with my FNB app using scan to pay. A few minutes after paying I was called to the back and informed that my payment did not go through. I opened my phone and showed the manager there my banking app which showed that the money had been deducted from my account. He kept insisting that I have to pay again because they cannot see the payment on their side. I refused to do so. Telling him if the payment by any chance reverses to my account, then I would come back and pay but I was not going to pay R3600. I told him I'd leave my details and take his and we would communicate if anything changes. This went on for over 30 minutes and was extremely humiliating for me and my family as they made it seem as if I did not pay.