Extra cost for fixing a service that can't be used

I have an account with ADT , and recently found out at the signal from my alarm is not being sent to ADT when the alarm is activated. I tried calling ADT , but they have informed me that they will charge an additional amount for fixing the signal from the alarm. So that means I am already paying a monthly fee to use their service, but I cannot use it when needed because I need to pay up more for fixing the signal that goes to them? Sounds like ***** to me.