just time to revisit this decade+ old thread.
Here's my solution to ending 99% of all nuisance calls: NOMOROBO
I was skeptical too, but after trying a call blocker with limited results and my fone was getting loaded with hang ups and calls from scammers pushing all sorts of agendas such as medical insurance (they always mention Obamacare), credit card offers, IRS settlements (I don't owe the IRS anything!), you name it I was getting it.
I saw a new scheme to deal with nuisance calls and signed up with NOMOROBO on my land line (well, cable fone service) and it was like a new day the moment it went active my fone was actually QUIET for days, weeks at a time. I told friends and they too now have found peace from 99% of the crap they were getting.
Note that htis is a free service for VOIP (cable phones service). Sorry but AT&T wants you to get all those scam callers on your copper POTS (Plain Old Telephone Service) so if you have conventional twisted pair fone service you are going to have to deal with nuisance calls with a callblocker, either a separate hardware device you insert in the line or your service provider may have a limited blocking scheme. You can read more about it at the NOMOROBO website
https://nomorobo.zendesk.com/hc/en-us/articles/205761775-What-Phone-Carriers-Are-Supported-
NOMOROBO charges $1.99 a month for cell fone blocking. And you have to decide if that is worth the resulting peace and quiet. To me the National Do Not Call thing was completely ineffective, these scammers use a random number generators or something to send out calls and a few are coming out of Canada, or show a spoofed number from somewhere they think is safe.
NOMOROBO lets a few charity calls through occasionally and I enter them their online system and add to the national database of calls to be blocked. Thats it!
DDH, having a nice quiet day! (and night)
https://www.nomorobo.com/