Refusing to cancel my policy

I had a policy with Netstar for my vehicle. After selling the vehicle, I informed them that I no longer owned the vehicle and therefore want to cancel my policy. I phoned and emailed 4 times since May 2017 but they didn't respond or process my cancellation and they kept debiting the money from my account. Eventually, last month I got hold of some Jeremiah who told me I needed to pay a cancellation/settlement fee, which I was happy to do but till today I am waiting for that letter which he promised email.

The annoying thing now is that I am getting SMS's about them taking me to debt collectors as if I ever refused to pay!!!