wanted a cash back

I wanted to get a cash back, and I was told by a cashier that in store they do not have money and their rule to give a customer R500 max and they do not even have the R500 in the whole store, I asked to speak to a supervisor where the cashier called Busie, who came with the attitude telling me to go to ABSA atm outside the store to withdraw, and almost everyone in the store was attacking me about the transaction they even made a coment saying I deposited money at the bank now I want to get it from the store, it was shouted the whole store as a joke that I wanted to withdraw money. Eventually after insisting on getting the withdrawal one cashier withdrew for me and the money in the till was a lot if they wanted they could have given me the R2000 I wanted. The staff was very unproffessional including the supervisor. I need to understand why they only give R500? My understanding is the bank has got an agreement with the stores to hive R3000 max cash back per customer. Your service sucks,