Non existent customer service / reply

I had an Altech netstar device installed in 2013. This year I bought a new car. I let them know via email on 2 occasions that I would like to cancel the service as I no longer drive the car with no response. I however still paid for the service. Now I just got another invoice. Yet again I rep**** stating that I have cancelled the service three months ago already. I will not continue paying for something I don't use! I will also not recommend this company to anyone as their customer service are non existent! I do not undderstand why they have a reply option on emails if no one on their side ever replies?! Pathetic (no) service to say the least!