Rude Cashier and Floor Manager

Wanted to pay my mom's DSTV at Kwikspar Arcadia, Cashier underpays without my consent nor seeking clarity after being initially rude. Wait for over ten minutes T the outside window without a word and then went to complain to the manager and the floor manager comes with attitude telling me to call dstv because it's a small mistake. Said manager does not great nor ask for my side but tells people on the line "it's 2018 and he won't be dealing with this" and rudely leaves the issues hanging. Humiliated and angry I go back inside the store to confront him and he raises his voice and that's when I raised mine and told him " *ck you" He swore back and told people about my apparent upbringing. This is totally unacceptable, you don't make errors and not own up to them and only make it's the customers problem. People with certain power must understand it comes with a responsibility, won't be seeing my money anytime soon.