Willing take your money even though contract expires

I signed up with netstar in 2012 of which I was told when i contacted them 2 weeks ago that my contract had expired in 2015. This was ok but it didn't stop them from debiting my account monthly for the next four years. I tried contacting their customer service and when i pose the question about the fact that i am paying for a tracking device that does not work, the call get cut. I got through another guy guy who tells me that I am due for an upgrade. Should I not have been due for an upgrade in 2015? So basically I have been paying for a device for 4 years that does not work. I have sent an email 2 weeks ago to their customer service email address and guess what - no response. Send another mail a week later and same story - no response. I did get a automated reply telling me that they strive to respond to all queries within 2 days ( What a joke this is). Will cancel my payments going forward and see if I have any legal recourse to get back my money. This is just pathetic service from this company.