Worst working experience

My worst experience was working as a cashier at shell overport motors Durban. I started working there on the 17th of December 2021 till the 20th of February 2022. It is a family store that is actually runned by 3 sisters named Muneera, Razia and Mariam they are soo rude towards their staff, Miriam once called me stupid for not knowing what to do when the scanner was not working and I was not thought. Razia also called me dumb because I couldn't find the coconut milk on the system she then realized later that it was not registered on the system she didn't even apologize she just registered the milk on the system and carried on like nothing happened. I never signed any contract with them except for the employment request form so I basically didn't know what my job offers and requires I couldn't even ask because they are unapproachable even the old staff is scared of them. I've been receiving short salary from my first pay till my last pay. I decided to ask on my last pay and I was told that I had high cash shortages off which it was not true I didn't have any shortages. I worked 8 hours per day and only had 15 minutes break, they extended the tea break time to 30 minutes when shell head office visited and changed it back to 15 minutes 2days after the visit. We pay for the store shortages while they come with their kids at the store and the kids will grab whatever they want without paying when they count stock and come out short we pay for the shortages. I was asked 3 times to work overtime and was never paid for those hours when I enquired I was still told about my high cash shortages that I know nothing about... On the 23rd of February 2022 at 16:38 I received a call from Muneera telling me to come to work by 18:00pm I was off for 2days and I told her I wasn't feeling well she said that I must bring doctors note when I come to work or else I will sign the warning I decided to quit there and then..She told me that she won't pay me for the days that I worked because I did not serve the 2 weeks notice that is written on my contract mind you I have never signed any contract. In my experience of working I have never seen such environment the basic conditions of employment act is not practiced I have never received any payslip so is the old staff. People are treated like trash there and they have nothing to say for they need to feed their families Shell South Africa please