Most people have received those annoying robocalls, which do not leave messages, or hang up on you if you answer, or offer you some some "service" or "opportunity" you are not interested in, or at worst are fishing for some information to allow your identity to be stolen.

The FCC is promising to be more active in monitoring the caller-ID numbers used by robocallers, so that services that block robocalls will have up-to-date databases without having to expend excessive efforts to compile their own lists:

American robocallers to be shamed in public lists
FCC vows to reveal latest names and numbers each week
23 Oct 2015 at 21:00, Shaun Nichols
http://www.theregister.co.uk/2015/10/23/fcc_robocallers_list/

I posted previously that I had started using a robocall blocking service, http://nomorobo.com, and I am glad to report that it has been very successful. It has blocked 95 of 103 robocalls over two months. I reported 7 of the unblocked numbers through NoMoRobo's online reporting form. The 8th call was spoofing a local residential number so I did not report it. Unauthorized caller-ID spoofing of an active third party number is a federal crime, but I suppose the law is difficult to enforce.

The NoMoRobo service (free to residential customers) works on "digital voice" landlines which have the "Simultaneous Ring" feature, allowing additional numbers to be rung when your home phone is called. Your home phone will ring only once if NoMoRobo detects a robocall. I have added a separate call screening device to my line which suppresses the first ring, so that I often only know I received a robocall because it appeared on the readout of that device; my phone doesn't ring.

I did see a report of another blocking service, RoboKiller, but apparently it is either still in beta, or not yet in operation, as they do not appear to currently be accepting clients.

Hopefully the FCC action will encourage more blocking services to start operations, since they won't have to expend resources compiling their own robocaller lists, as NoMoRobo has had to do.