As for Verizon not blocking the number without charging you. Why not just switch?
Plausible, and kind of works, except when you get regular phone calls from real people whose numbers you don't yet have in your phone. Luckily, this would likely work okay for my mom.
> register on the donotcall list
Which I'm sure Indian call-centers respect.
(Sorry to keep harping on the Indian call-center thing, by the way; I don't mean to show any disrespect to any Indians, but these things do seem to operate largely out of India, much like the 419 scams seem to be forever embedded in the cultural mindset with Nigeria.)
> Why not just switch?
Two year contract that's expensive to get out of.
My advice to her was to report the calls as harassment to Verizon every time; I believe they can't charge you to block harassing calls.
One obvious thing they can do about it is pressure the phone companies to stop allowing caller id spoofing. It isn't hard, if the number is from North America, then the phone companies verify it (if it is from a cell phone overseas they have verified the phone and should have verified the owner of the phone), otherwise it is fraud.
Caller id spoofing exists so companies with a private switch can have a bunch of different phones have the same number- but the phone company knows what numbers the company is allowed to use so the rest can be filtered.
Mind you the above will take a few years to implement. However nobody is working on it because if even one party that needs to do work doesn't the whole thing falls apart.