I don't get many of these anymore. Every time I do I pick up and harass them. Then I keep calling back for as long as the number works.
On a more positive note, Hiya has been working really well identifying spam/robocalls, so I don't actually pick them up.
Robocalls generally seem to be going through the roof.
It's not a lot more effective though.
"This is the IRS speaking" in a voice about as authoritative as Microsoft Sam.