Terrible service and rude cashiers

The treatment I received at a shoprite store in Arcadia Pretoria is beyond despicable, I had to wait in a not too long que for over 20 minutes while the cashier juggled working slowly and chatting with other staff members. I politely asked her to serve us and do it faster to ensure better service and avoid making myself and other wait for service any longer however the cashier lost it and told me that my being a customer has nothing to do with her and that I'm not the only customer waiting for assistance, why aren't the other customers complaining. She furthermore told me that the card machine isn't working properly so what must she do, I asked her to please respect me and other customer enough to inform us or call the manager to help her, she then continued to be highly rude and passing remarks. I was so offended I went to the manager to request a refund after she gave a torn R20 note as part of my change. The managers all kept leaving for long periods to call her making me wait even longer for assistance without processing the refund. This experience led me to feel that I never want to shop at the supermarket ever again and so should everyone because the cashiers and senior staff don't treat customers right.