I have had the same phone number for 15 years, and I have been getting A LOT of robocalls lately.
I tried stopping them with NoMoRobo on iOS. It worked OK, but it can't match "Unknown caller" or blocked numbers, which made it kind of worthless for me. Sigh.
Nomorobo has been hit/miss for me. 75% on catching robocalls, and I've had a false positive that belonged to a caller I wanted to talk to. I'm not enthusiastic about the results, but will be continuing to use it.
I was just poking around in the settings for my new Android phone and found Settings > Applications > Phone > Call blocking > Block list > Block anonymous calls. Would that be helpful at all? I haven't tested it myself.
I tried stopping them with NoMoRobo on iOS. It worked OK, but it can't match "Unknown caller" or blocked numbers, which made it kind of worthless for me. Sigh.