No response cancellation department

We sell our car Nov 2019, I try and cancel my policy, I send 2 emails to their cancellation department, but still I pay for my car, Its almost 2 years later. I phone them aswell, but still no response. Im not happy. Who can help me? I will not recommend them. Everytime that there is a problem with the sold car, Netstar phone me, I tell the person the car is sold,