ADT is a waste of money

I would have thought the purpose of getting Armed Response is to make sure you are safe. Yesterday our alarm went off due to my mom opening a door while the house was armed. The alarm went off, they called me, by the time I got to my phone the phone had stopped ringing. They called my mom and by the time she also got to her phone it had also stopped ringing. I then assumed they would send armed response to check if everything is okay. To my surprise, no armed response but a call from them 15 minutes later to check if everything is okay. A lot could have happened in 15 minutes. If it was a real emergency we could have been in danger. I need to cancel my contract as their services are clearly not what I signed up for.