Store manager refuses to exchange my purchase - Consumer Complaint for Clicks Store - Head Office

I bought me a toni&guy straightener at clicks in Promenade Liberty Mall on the 27 October 2018 , I used the straightener for about 1-2years .I started having problems with the plate that shows the straightener's degrees ,the degrees were not showing at all .I went to clicks and when I got there the degrees were showing on the plate , I explained to them that perhaps the straightener is faulty but they said they can't assist me with exchanging my straightener ,I had to keep it . A year later I had issues with the straightener again.the heat of the straightener was not consistent, it would be hot but the temperature would drop without showing on the plate , I explained to the manager and assistant but they refused to exchange the straightener, I kept explaining to them that it was my second time and they refusing me again . The sales assistant said to me that I cannot buy my appliances at clicks and use it for my home-based business , I explained to her and the manager that it was not a business that I had but I had a regular that would come an do her hair by me , she kept saying that "her appliances is not used for business so she will not help me" i asked her why is it that I have a 5 year guarantee when I can't use my guarantee, I told her that if it is my second time coming to exchange then it should mean that the straightener is faulty , the sales assistant and the store manager plugged the flat iron in for about 3 minutes and said there is nothing wrong with the heat of the flat iron , when I explained to them that its a short period of time and the heat wouldn't show immediately they said they cannot assist me. I'm at my wits end and really feel like this is poor customer and business service.