I see where others have complained about this incessant caller and Here I just posted my comment and 15 minutes later they called again, I blocked it the first time. Now I will block it through my Comcast service so I don't get the one ring.
Caller ID showed up as "L7 SRVC CALL". I didn't answer and they didn't leave a message. This is the first time they have called.
A personal recommendation: DO NOT ANSWER ANY CALLS FROM ANY UNRECOGNIZED/SUSPICIOUS NUMBERS. This will only encourage them to call you back. Also, don't try calling the numbers back to request a DNC (Do Not Call), because many of these companies/people will not comply. Finally, blocking numbers is probably useless since these people have tons of numbers. The best solution would be to ignore them and they'll eventually stop calling (at least it works out that way in my house).