Poor customer service

I went to the chatsworth store to purchase the 2 large pizza special. I made payment via my debit card and it went thru via my bank (received confirmation sms) however the cashier said it was unsuccessful and I need to pay again. So he explained it was a network error and I can speak to the manager so I said it's fine I understand and I am well aware of situations like this. I made payment again and then went to the manager and asked him to give a copy of the unsuccessful payment and asked him to please write his name so I remember when I do come with proof (bank statement) who was at the store on that day. Hassan(the manager) starts screaming at us saying it's an error and we can call his boss and speak to him whilst we are still trying to explain to him that we understand all we wanted is his name on the slip. The manner is which he handled the situation is pathetic considering he is a manager he suppose to act calmly. It seems as we switched roles and he was shouting whilst we were calm. I'm sure that is cctv footage to back what I just said. It was embarrassing and it's the first time I experienced this at the store. Very disappointed.