Harassment and threating collection calls

I have been a client for car track for almost two years. I requested the to cancel my membership with them September 2023. The reason for canceling was for the poor service I am receiving from them (car unit was not monitored). I spent almost 6 months with hopes that I will get confirmation for the cancellation. I am not receiving harassment calls and threating call that they will blacklist me is I do not pay a certain amount. I do not need car track contract because they failed me.