Almost never respond to emails, slow follow up when they do

Having bought my car with a Beame tracker I never had an issue. Payments went off, car never needed tracking. 7 years this went on, month after month. I sold my car and no longer needed the service so I requested it to be cancelled via email. A week later I get a message regarding a telephonic conversation I never had. When asking about this conversation my email was ignored. Another week later (in the new month) an agent calls me to sort out the cancellation with the consequence being one more payment. I stopped the debit order because I'm fami**** with these things dragging on. Wanting to just be done with this I agreed to pay the final amount, which I was told could be debited from my account. 2 weeks later I get a notice to state the account is in arrears. Another email sent to ask for clarity (must I pay or will it be debited?), another email ignored. Another 2 weeks later I get a final notice. To be frank, this is BS. I was told it took them 2 weeks to follow up on my cancellation because they've had a lot of cancellations and a backlog developed. I am not surprised...