Employee refusing to deliver service

A specific employee (Susan Nel) had on two occasions been extremely rude to me and tried to belittle me in front of other customers. The first time(6/1/15) I went to buy a pre-paid simcard, at first she ignored me, then complained about my documentation, and then finally announced to the whole store that she thought I had been black listed (even though its not true). At my second visit (12/2/15) to do a sim-swop, this same lady once again found fault with my documentation. I told her that these same documents were accepted at another store where I went the last time when she refused to help me. She then continued to request the sim-swop on the system, but when she completed it, she refused to give me my new sim card. She told me I should bring an affidavit from my landlord before the sim would be handed over to me. I told her that I would not be able to make it back that afternoon before they closed and that the next day would be working late. She told me I should come back on Saturday and that I should just go without my phone until then. I then phoned someone to ask what I should do. During the call she was shouting at me that I was lying to the other person. I'll never go back!