If you want support/service/monitoring by someone not you, security companies do have a purpose. Depends on your situation though.
(Arguably, these discounts are things they trust you at your word for, but perhaps if they're not satisfied they're true during a claim, they might use it as a reason to not pay out.)
Also, the discount is for central monitoring, not merely having a system.
I'd reread your paperwork if I were you. It sounds like you could have falsified information, and effectively have no insurance.