Refusing to replace nonworking stove

I bought an electric/gas SMEG stove from Dion Wired in Centurion Lifestyle Centurion on the 30th April 2014. I used only the two electric plates from then till November same year reason being that my house didn't have a gas installation. I only had the gas installed towards the end of November. The guys from the company that was doing the installation mentioned to me that the stove's knobs were not turning smoothly I must report it. I reported it soon after that to the Dion Wired store and they said they would report it to the manufacturer that is Smeg and they would come out and inspect. After making several follow up calls a technician finally came to the house and informed me that the stove top has shifted forward which is what was restricting the knobs from turning normally. The stove's electric oven also does not work. It causes a power trip every time you switch it on. Smeg is unwilling to replace the stove and I have been treated very rudely by their manager named Thinus de Beer. They say it has cosmetic defects which to me is troubling because the stove is not working and yet they call it cosmetic. They also say I took too long to report it. The stove has a 3 year warranty.