Horrible Customer Service

Called them two weeks ago trying to arrange for them to install a new device on a vehicle I have purchased; actually I had a unit but I sold that vehicle so I just wanted them to cancel that unit and install a new one on my new car. Sent them several emails and they never responded. They called me last week Friday to tell me that someone will call me to arrange for fitting of the unit till today I still have not received that call. I sent them an email again today, and they still did not respond. In the meantime, I am driving around with a car that doesn't have a tracking unit, but I am actually paying for it. So annoyed and tempted to cancel the contract..