Robocalls

Over the last few days I have been inundated with "You've overpaid your utility bills so press 1 if you're a sucker" robocalls.  I report every one of them to Nomorobo.   All the calls come in with unverified (naturally) caller-IDs.   Is there some technical reason that Cox can't implement an option that blocks all calls with an unverified caller-ID?   This is beyond annoying.