Bad service with no thoughts behind it.

I have been with cartrack since 2013 when I bought my car and ever since I had no problems with them until recently. Every month they would send me an sms to let me know that my unit has be tested and I noticed only in September that the unit might not be working bcs when I took out the battery in the cat they never called me and usually if that happens they would call. I took time and phoned to find out where my car was to test the unit, however according to the system they could not see where my car is. So I noted that I was righ by saying their unit was faulty. So asked them when can they come fix it because clearly I have not been unsafe since September or even earlier than that and they have been taking their premium monthly without fail. I asked the guy whose jib is it to check monthly that the unit is not working and inform me if the unit is not working and I was told it's not their fault its not working but part of their job is to test it on a monthly basis. And I decided that this service was no longer useful to me and I canceled and they did not even ask me why I was canceling. 7 days after canceling, I get a call from a lady asking when am I going to pay cancelation fee. No one told about any fees and why should I pay for something that was not working? I've always been a good paying client and I think now cartrack is taking advantage of that. Their cancelation fee they can take it from all the premium that I was paying for even when they were no use to me.