No deals on voice packages and continuous changes

Last week Thursday I went to the Cell C store in Tygervalley. The gentleman told me that I can get the Hauwei Mate 7 on the Straight Up 200 for R505pm. I wanted to take this but they had no stock and no other store had either so I said I will come back. Today I went and they told me its no longer available on that and that if I want a deal on that phone I must take the SmartChat, which has no minutes and the out of bundle rate is insane, or I can get it on the Straight Up for R800pm which is ridiculous. I want to know why and for what reason?