Poor service

They fitted tracker in 2021, which never worked on my car and called technical guy who did it as he said I need to call him when it's not working and it worked and got numerous call from ADT promising to escalate the case but to date they never did anything the only thing they want it's their money regardless of it not working and reporting to their technician, until he blocks me. Then i decided to reverse all my premiums now the they take me to collectors without even receiving single feedback from management. Now they dont want to take accountability of their technician, they say I should not have called technician but them but technician said I should call him and he will escalate it. To date nothing done until I sold me car, then they say they want their money regardless of them sorting the problem