Appalling Customer Service

appalling service from the waiter at Wimpy East London Hemingways Mall. Asked her questions with regards to the app before i paid she gave me attitude and forced me to pay and threw away the slip before i could even pay or scan . I asked her why did she do that , she walked away and I called her while she was cleaning another table and said i am still waiting for that slip she threw away, she went to the lady at the till and without noticing i was behind them, 3 ladies were saying awful things and i went to them and told them what had happened. the waitress walked away again. No apology none whatsoever. If Wimpy doesn't train their employees to assist customers with the app then why have the app to start with.