Cheap computers, and poor after sales service

I purchased a Laptop computer from Dion Wired in Cradlestone mall. The laptop was on special, and it cost me R3,999.00 ZAR. According to the sales person, the laptop was state of the art, and would suffice for surfing the web, and any school work. Unfortunately, the laptop in question was the worst purchase I have ever bought, because the laptop is a cheap unit, and is very slow. I took the unit back, and even though they could not get it work, they believed that's just how it is, and there's nothing they can do about it. I was made to leave with my unit that still doesn't work well at all. In my opinion, Dion Wired in Cradlestone are selling cheap laptops, without honoring their word. I have since been unable to use the laptop, and despite talking it back the 2n time, they still cannot assist me.