Still paying for Cellphone Insurance

I was sold a mobile phone by MTN over the phone. I received the phone and was contacted and sold phone insurance over the phone by Fonesure. They did mention that it would be easy to cancel it if I no longer needed it. Surprisingly I never got the policy and have never heard from them ever since. I don't know the T's & C's of this insurance as I never got even a single document . I have paid premiums for around 3 years now. Bearing in mind that I have already paid up that Phone and no longer have a contract with MTN. The number I got to reach Fonesure doesn't get answered. I just want to cancel this Insurance. I don't even have the phone anymore but yet I am still paying Insurance.