Rude and disrespectful behaviour

I visisted MTN West Coast Mall today and was apalled at the customer service I received from Carmen and Azri. I went to enquire about increasing the memory of my cellphone. I was confused as to the sim memory/storage itself and did enquire quite extensively about the Gigabyte and Kilobyte difference on the sims of phones and the actual memory card. They could not really provide an explanation on the difference between the 16k sim and 32k sim though. We eventually agreed I need a memory card and I accepted. I was told to wait for 10-15 min. I went outside the shop and returned short while later to retrieve my shopping trolley. Carmen and Azri did not realise I was inside the shop and I overheard them laughing and joking about my "ignorance" (" the more I told that woman it has nothing to do with memory, the more she argued with me") This was in front of other customers sitting in the shop. Needless to say I confronted them as to why they make fun of my so called "ignorance". I felt belittled and was disgusted to think that this is how they talk about their customers behind their backs. Utterly rude and totally disrespectful. And then to learn Carmen is the "Supervisor"??????? Already switched to Vodacom, thank you Carmen and Azri.