No 14 day Money Back Guarantee

We bought a Genesis vacuum cleaner from N1 City Verimark on the 03/10/2015. We previously had two Sharkys which worked. We were informed that they have a refurbished model which carries the same guarantee as a brand new model. After fully charging the vacuum we found that it worked sluggish and did not pick up all dirt or dog hair as advertised. On returning the vacuum on the 13/10/2015 the sales assistant tested the vacuum on the shops floor. The shop does not have a carpet but tiles. We use the vacuum on a carpet. My Mother in law got sent away with the message that the item does work. My wife phoned Verimark Head Office where Thabo once again informed her about the 14 day money back guarantee. He sent a email to the shop and informed my wife that we should take the item back on Saturday 17/10/2015. Why was the item not replaced or money refunded when we visited the store on the 13/10/2015. This is very poor service. I want a replacement or my money back when I go back, at my expense on Saturday.