Bad customer service

Please don’t sign up with National Security & Fire, I have been with them for over 3 years and have had minimal issues with them until I had to cancel because our suburb have a preferred security company that they have a agreement with. Now I am all of a sudden owed a sum of money which I had paid already. They now being sour about me leaving & now want to suck money from me for my cancellation of service. Beware to anyone who wants to sign up with them.