Not responding to a request to cancel insurance

Up until November of 2014 I had insurance on my cellphone through my service provider. (used to be Nashua Mobile and then I got transferred to MTN) During November I took out home content insurance through Santam, and they quoted me a lot less per month on insuring my cellphone, so I went ahead and insured my phone with them. Subsequently I contacted MTN to inform them about this and requested that my insurance through them be cancelled. This was early in December 2014. At the end of January 2015 I eventually received a response stating that my request has been escalated to the correct department. Since then I have sent a few emails to [Email Removed] enquiring about my request. I still have not received even ONE response back from MTN. It has now been 6months and I am still paying for insurance with MTN which for 6months long already I do not require. Every month MTN just adds the fee to my bill. I am sick and tired now of waiting and not receiving response. And I feel that MTN owe all of that money back to me. Because in December 2014 I requested the cancellation and for 6 months already I have been billed for it. This is ridiculous and I am a very unhappy customer.