Fidelity alarm system cancellation unsuccessful

Not happy with fidelity-adt alarm system. I request for a cancellation. I was given an email to state my cancellation reasons , I did that. From there I haven't received any feedback. I tried calling 3 times and I was told someone will call me back . Nothing until now. I find it difficult to cancel and the system is disconnected as I was told it is not fixable and it never work from day one of installation. I need help to cancel the system and I would like to have all my money paid as the system was never in a working condition. Thank you