Who called from 5624516742

Received a call from this phone number this afternoon.  I answered the phone but there was no sound at all.  I called the number back (after disabling my outgoing caller ID) and a recorded message instructed me:  "Thank you for calling back.   If you are not interested in receiving any future calls regarding our special promotions and would like to be placed on our do not call list please press '1' now."

If the caller does nothing the message will continue to repeat.

I pressed one and after a brief delay the following message was generated:   "Please allow up to 72 hours to have your number removed from our preferred marketing list."  The call then disconnected automatically.

My question is how does a company know what phone number to remove if you block your phone's caller ID?  I suspect they just want to confirm the phone number.

Recording (trying to sound like a real person) offering a "free" security system.

Got a call earlier this afternoon from this number, let phone ring 3 times, picked it up, said nothing.
The caller said nothing. Several seconds later the caller hung up.

Name              Number               When                        Length
ALARM CO     562-451-6742     Tue, Jun 30, 2015     0:13

Received call, automated, trying to sound like "real" person, offering a free GE Alarm system. Tried to get real person, and said sorry to bother you, we will place you on our do not call list.  My number is on the Federal DNC list for years. Any idea how to find and sue this company?

CID showed Alarm Co.  Figured it was another telemarketer or another scam, so I didn't pick up. No message left.