Poor and rude customer service

Hi. I visited KFC in Plumstead Cape Town earlier. I ordered a 9 piece chicken meal. The teller then quickly rumbled off if I want to donate R2 and something about if I own a vodacom number. Both these were asked so quickly that I said both no to both without paying too much mind. Afterwards I saw a notice board indicating that if you have a vodacom number and you spend more than a R100 that u you receive 250 mb of data. I then asked the fellow behind the counter lady to please give my slip to the one teller who helped me and ask if I can please still get the data ( other tills had no teller at all.). The teller the shouted loudly so all should hear and stare at me, that she did ask me and I said no. I then apologised and said I didn't notice the data reward and the crux of the matter. To which she shouted again but I told you and you said no. I then asked politely if she can assist me still. She said she needs my cellphone number, but I then being polite and noting her tone said she can help the current customer first. The teller then however continued to ignore me and never provided me with the data. I left KFC embarrassed at the shouting and negative attention given to a customer who made mistake in terms of a noted reward.