Struggling since October 2014 with defective goods

I bought a defy double door stove from OK in Paarl in 29 April 2014. I have had problems with the stove and defy has been out twice. I have had endless problems with OK with regards to the stove. They will not replace it and insists Defy must fix it for me. The point is I bought the stove from OK directly thus OK should fix the problem and not pass it off onto Defy. I am at my wits end as to what to do as I have almost finished paying for the stove yet it is defective and damaged. I have made several calls to OK and Defy and it feels as if I have been sent from pillar to post. All I want is for the stove to be replaced as it is less than a year old. I am getting absolutely no joy from anyone and in the mean time the oven does not even work properly. Any assistance with getting this mess resolved will be greatly appreciated.