Terrible service

I get to CL Alex Mall, I’m busy sanitizing, so lady comes in the store and cuts into the front and teller served her before myself, she didn’t bother to sanitise. So I get to the teller, whilst she taking my order, she also chatting to the colleague,?she noticed that I was annoyed and apologized, and somehow she decided that I ordered Fanta, as per my receipt.when my order is ready. I go to collections, I ask the lady not to tear the slip because it is part of paperwork but she bluntly looked in the eye and tore the paper, she tells me it procedure and this is how things are done here, I can’t complain all I want but she will tear my slip even next time, but I asked here nicely and she exuded a bad attitude and wasn’t even bothered, I asked got her manager who backed her slip tearing story telling me that it is from Head office, but only in the hood this happens. The manager delayed was she was debriefed, It was a bad experience and I didn’t even enjoy my meal because of these events. What I don’t understand is, why is the manager siding with bad service, habouring rot, I mean she apologized under duress n printed a new slip, and was giving me a vibe herself, why are they defensive? Bad service is bad service regardless of us trying to please our colleagues