MTN not honnering insurance and do not respond to request to cancel insurance.

I have a Nokia phone on a MTN contract with insurance. The phone developed a charging defect. I contacted MTN and submitted the required forms. They contacted me by phone informing me that I waited to long for the claim and that they will thus not repair my phone. I asked them to cancel the insurance because it was useless since the phone is not working. This did not happen. I requested cancellation of the insurance again via the "contact us" feature on my on line account on 2018/11/06 but did not even get a response. I have again requested the cancellation of the insurance on 2018/12/01 and are waiting to see if I do get a response.