Cancelation Issue

Had to get a tracker from them through my insurance. When I sold the car I canceled my account with them online. I got an email acknowledging my request to cancel and stating it is being handled. Two months later they phone me due to outstanding fees. When I told them I canceled my account, they had no record of it and I had to send them the email stating that my request for cancelation is being attended to. Which would write off the outstanding fees. I sent it trough. Now another two months later they are harassing me again about my account. When being told I canceled it months ago they just put the phone down in your ear without saying anything. There operators are rude and unprofessional.