Vodacom device cancellation

I'm furious with the non competent service I've been receiving in regards to my device insurance cancellation which I did 3months ago and still being billed for it, I've made several calls and it's different stories from each consultant, what one has to do to have their contract cancelled,this will lead to me refusing to pay further more which will affect other services I'm using and dont mind paying for, pls attend to this matter.