I purchased a home (April 2016) that had a very sophisticated ADT system with all the bells & whistles (pun intended). The prior owner had installed it in Jan 2015 and signed the standard 3yr agreement. He probably paid a huge penalty when he moved.
All I wanted to do was sign up for monitoring of my ADT system on a month-to-month basis with no extended agreement.
ADT initially said I couldn't do that. Then, after I told the sales guy that I was going to install a Simply Safe system, he suddenly was able to waive the extended agreement. But when the installer showed up, I suddenly needed $250 worth of equipment (for a 14mo-old system that had been working just fine for the prior owner).
I sent the ADT installer on his way and ordered a Simply Safe system.