Unhappy Customer

Good Day, I had very bad experience at Game Store in retail park beacon bay. I purchased 2 packet of Doritos which said buy 2 for R28, 99 or 1 for R21, 99, when i went to the till it did not scan that price. This was not about me looking for to get for free but the principle behind the advertising in the store. I took the cashier to show her the sign where the chips was in front of major appliances. She called a coloured lady to speak to me firstly who was very adamant and rude as i am a consumer. She said i need to read the pamphlet as it says 1 simba chips and 1 Doritos for R28.99. My wife and i walked in the store which we do every month and do our shopping i dont read pamphlet before shopping. I requested to speak to a manager and the short coloured lady that was speaking me said she was the manager. Her approach and the way she spoke to me did not show at all any management s****s. I myself working in the gaming industry and deal with customers every day of my life and being a manager not once did i ever approach and speak to any of my customers being them wrong or right. Any which way by then my wife was exhausted being us shopping from early that morning we paid the price of what scanned but the point i was trying to make was change the sign to prevent other customers like me being unhappy. The lady also mentioned that game can not put signage up specifying that we need to 1 take different chips which in this case was one Doritos and 1 simba chips. I was very unhappy with the way i was spoken to as i felt insulted that i can not read or i must read a pamphlet before i shop? This is not a good explanation and i am very unhappy. Please double check all your price set ups before opening your store every day. Thank You and Kind Regards