If you can, try NoMoRobo. It's available through both VoIP and Cell (not sure about regular landlines). You still get the call, but NoMoRobo runs the incoming number through a list of known robocallers. It will then answer any offending numbers and force them to pass a test that requires human interaction. If that test isn't passed, it hangs up. The phone will literally ring once before it does this, and that's that. Unfortunately some groups (political mostly) do get a pass, but that's due to federal law (same reason they and churches can freely violate no-call lists. Blame cold-call lobbyists.)
This won't work against most scammers, who are instead humans (usually outside the US, but not always). But those groups aren't exactly eager to abide by the law anyway (they're already committing a federal felony--wire fraud--so what do they care about a fine?) And that's assuming they aren't calling from a country that harbors those types against US prosecution.
If you're worried about NoMoRobo, it may (or may not) help to know it was handpicked in 2012 by the FTC out of a number of other apps designed for this. They felt it was the best. But yeah, that depends on your level of paranoia about/trust in the feds.
