I've moved to a new geographical area a couple times in the last few years, but always have kept the same cell number. Since I have zero connections with the area my number is from, it's really easy to pick out when it's these recent robo callers that spoof the number to look like something local. If the area code and first three prefix of the number match my own, I never answer them and then add the number to the blocked caller list.
There really needs to be something done by the carriers, phone makers, and gov't regulators (ugh) to nix these assholes, because the blocking capabilities of today's phones are pure shit and the government's enforcement capabilities of the laws are even worse.