Netstar - Worst decision I've ever made

Our experience with Netstar is ridiculous.

We use our tracker to check up on our workers vehicles every so often. Only to find out when we wanted to view a report that Netstar had not actually worked or been tracking one of our vehicles for approximately 4 months. Netstar was not even aware of the fault. We asked them to check all the devices that they are all in working order as 3 of the vehicles devices are pretty old and we wanted to make sure everything was working. They eventually came, but to actual speak to the right person was impossible as you go through a call centre which makes it extremely difficult to plan logistcs around when a technician is available. As if our trucks are just waiting for Netstar instead of in operation. They eventually came but it was a painful process. We wanted to cancel our Netstart approximately 2 months ago. Do you think we can get any response from them? We have even gone into the local office. Eventually we spoke to a lady who told us we are in a 3 year contract with all of our vehicles since they upgraded our older devices. We were not aware of any upgrade nor did we sign anything. We have sent further mails informing Netstar that we will not pay going forward and have cancelled the current debit order with our bank. We have requested a removal of all devices. And yet again, no response. I want nothing more to do with Netstar. And I will not pay them anything more. They are welcome to come and remove any property that belongs to them on my vehicles. I have no clue how a company like this operates or still exists with this kind of service.