Wrong quality of sold laptop

I bought a HP I7 for myself as a student, due to the work load I require a very fast and reliable laptop. I went to HP in Sandton City where a gentleman( whom I was told no longer works there) sold me a laptop. I had to go withdraw money at the ATM as my card wouldn't swipe the amount. When I returned I saw that they had the laptop out of the box, which I thought was normal as they were going to show me that nothing was wrong with it. Not even 2 weeks after purchasing the laptop for R10 000, the screen just went blank and the computer was on but nothing was responsive. Due to myself living far away from Sandton, I sent my mother to go complain; she was then told that I was aware of it being a demo (THIS WAS NOT THE CASE AT ALL!!!) HP refused to give me a new laptop, and rather fixed the laptop, I accepted it, mostly because I ha no other option because I wasn't there to fend for myself.. within about 6 months(if that long), the same thing happened again, I went to discuss it with management at the store, and was then told that I should've asked for a new laptop when it happened the 1st time (WHICH MY MOM DID!!) I was then told that HP has a policy where if the same incident occurs 3 times, that I would receive a new laptop. I then questioned it by asking if my warranty expires does this still apply, and I was told that it does due to it being HP's policy.

needless to say that it happened again not long after the last incident, and now my laptop was out of warranty and I went back and it was just bluntly refused to give me a new one because now HP had apparently changed their policy, and I had to pay R2000+ to pay for my motherboard to be replaced. I refused to pay this because HP has given me nothing but issues regarding this laptop, I then took it to get fixed somewhere else.

I am so disgusted in the service I received, I went in there asking for a brand new laptop and all I got was utter hell with no co-operation and nothing but excuses! Management spins stories among one another to keep their asses safe, but nothing gets done about the customer forking out tons of money( of which I do not have an over supply of).