Poor service faulty tracker

I took a tracker from this company cartrack on February, they installed the tracker but it was faulty. The technician left without advising me how to track my car on the App I was supposed to download. I then downloaded the App and typed all information required but all I could see was nothing dololo regarding to the position of my car. I then emailed them telling about the faulty tracker they informed me they would come repair it in March, it is now July. I have been sending them umpteen emails but they don't respond and they had the audacity to call me this week offering me a car insurance whilst I'm still not satisfied with the first thing I took from them. Least I forget that every month you deduct from my account for nothing, I'm basically paying you for nothing. I am tired of running after this company, if it doesn't reinstall the tracker this week best we cancel the premium