I lucked out and got a cell phone number that gets very few calls. Lately I have been getting calls for a "Sandra" (not my name) from a specific number. I finally caught one and told him, No Sandra here. He said he would take the number off his list. I have gotten 3 more calls from the same number in the last few days!!
Number blocking is pretty useless as the bad guys can spoof numbers -- look at it this way - if you get a call from your own phone number, you know it is spam, so ignore it.
This is my favorite response to spam calls. It is a "bot" but the spam callers take a lonnnnng time to realize it, sometimes up to an hour. Look up "Hello this is Lenny" on Youtube.
https://www.youtube.com/watch?v=fXf_oA9KT_M