Yes I did try NOMOROBO but I'm still getting calls with NO call back number. I actually bought ($50) a product called Call Blocker and it has eliminated approximately 60% of the calls. It's just so annoying and invasive. I think it borders on bullying and harassment. I think a good lawyer could make a good argument for that!!!
I hear ya!
You can set things up here to block "anonymous" calls. Is an anonymous call the same thing as not having a call back number? Looking at my settings it's defaulted to do that already. Have you checked yours to make sure it's enabled?
There are already several state and federal laws on the books that make many robo calls illegal. Unfortunately, they are pretty much unenforceable when the calls originate from out-of-state or out of the country.
I think the only real solution is for the phone companies (including Comcast) to stop these at the source. I'm sure they must have the technology/equipment to do it, but it's just not in their financial interest to do so at this time.
Maybe we'll just have to wait for some Silicon Valley genius to come up with a new 'disruptive' gizmo/buisiness that will solve the problem instead (like your Call Blocker product, only better.).
In the meantime, I'm using Nomorobo myself and it seems to be working ok, but then again I'm not getting blasted with robocalls several times a day. My phone will do the characteristic single ring maybe once every couple of days or so. I could understand where it would get old pretty fast if it was doing that several times a day!
Anyway, good luck with all this. If you find something that does work well, please come back and let me/us know!