Cancel my contract

My contact expired in September the consultant contacted me about the upgrade I didn't want to upgrade instead I took a monthly airtime for 140 for the two phones but to my surprise when I received the bill which they have charged insurance of R652 for all phones which I didn't know where it came from, immediately I called them and they said it will be canceled,but was never canceled. Last month I went to Voda world, where the consultant told me that they will cancel the insurance and refund my money back on the 15th of this month but I received the invoice this month they are still charging me. I am tired of calling them please cancel my contract.