Look, it either IS or IS NOT Alarm.com. There is only one way to find out - sue Alarm.com on the basis of the statement that the caller is an agent of that company and as an agent, the Principal is responsible for all of the agent's deeds (this is Common Law going all the way back to Merrie Olde England). See what their defenses are, and if they want to interplead other defendants as the real responsible party that is their right.
All I did was go to Alarm.com and here is what I found - the company's real name, address, telephone number, direction how to get there and on a different page in their web site their whole corporate governance, quarterly profits, K-10 filings and who knows what else.
The bottom line is that if you do at least the minimum amount of research, follow through on it. If they tell you they represent a certain company, find that company and ask them.