Called me 4 times on the 1st of September and then again today twice already (It's only 1:45pm). I never answered and no message was left by caller. I have blocked this number now.
Answered a call from them about an hour ago. Guy offered the security system angle, we responded we just installed a security system and he said "Good for you" and hung up.
I guess, unfortunately, by even answering and speaking we've confirmed it's a live number.