This is not thieves, they are an ADT dealer offering a free security system in exchange of putting the ADT sign in front of your house. They came to my home and the agent was very professional and I got a great deal. We are now secured by ADT. Installation was done the next day. Great company! I recommend it.
Yes it is theives. They sounded legit and set up an appointment promising to show credentials and then didn't show up which made me suspicious. I called ADT and asked their sales team if this offer was affiliated with them and they said no it wasn't them who called. They caledl and ask lots of questions about the existing security system. As a result we will now be reactivating our monitoring with another company.
Ignore the fake ADT cheerleader above, this is indeed a scam. Hang up, under no circumstances allow these people into your home. They are thieves. They are NOT ADT! If you want an alarm system, call an alarm company. Never respond to calls of this sort!