Appalling treatment from Sky City after Engen 1app malfunctioned

I went to the new Engen garage in Sky City to fill up earlier this afternoon. I told the attendant that I intend to pay with the Engen 1app just to be 100% sure that their system works before I could fill up because I didn't want any problems. The attendant said it was fine and that I could pay with the app. Electricity went off before he could start putting petrol in my car. I waited a few minutes for the generator to kick in and for the system to reboot before he filled the car. When he was done, I tried to pay with the 1app as I had stated up front. For some, reason only my transaction was not on their machines. This he said, meant that I could not pay for the petrol with the 1app and to pay with either a bank card or cash. He said even the cashiers couldn't help me in my situation. I stood there explaining that I had mentioned upfront that I will be using the 1app to pay for petrol was because I didn't have any cash or money with me. No one would hear of this. It was such a humiliating experience and I felt like I was being treated like a ********, even though this was not my fault. I used someone's card to pay for the petrol eventually after 30 minutes of arriving at the garare. Engen 1app never, ever again! I don't get why Engen would keep on promoting it. In December at this very Engen, there were ladies that were promoting this 1app.