Bad client service and amateur handling of my account

Well I asked for a security system only for them to use my OLD original system...After about 2 years, I guess, I noticed that they were charging me but no tests were being run AND I never had an alarm going off...I then decided to test MY OWN SYSTEM and her is where I established, through an ADT technician, that the battery was flat and that they NEVER gave me a new one, hence no alarms ever going off...They changed the battery but NEVER came to see me to re-establish the account FROM THAT DAY...Now 3 years later, or so, they are still expecting me to pay my bill and I flatly refuse...Their client service also leaves a lot to be desired as they simply do not care about my problem.