Mr Price Greenacres, pathetic service!

I have never felt so disgusted in Mr Price Greenacres. I have a dual account with them and I have been purchasing there for many years. I was very young, still on school when my mom decided to make a dual card for me. For the very first time today, the cashier told me my signature does not match after using this card for many years. She refused to phone my mother who is the card holder. She then said my details has my mom's ID number, but all the time it was right as I was the only one purchasing most of the time. She kept raising her voice and basically claiming it is *****. I was never humiliated like this before as customers kept staring but I was a loyal customer for many years. The manager then came and also raised her voice claiming her signature remained the same all her life. I would like to know how I could always purchase without it being a problem before. The cashier and manager had absolutely no etiquette. The cashier also then refused to give my card and then refunded the clothes claiming I could leave, she would just write a statement to head office. I was utterly disappointed and embarrassed. I would like to find out if there are further steps I could.