I have heard rumor that if it is a robodialer, you can answer with complete silence,  saying nothing and no background noise....If no noise is heard, was told the robodialer will mark off your number as dead. Not sure if true or not, but worth a try, because these people are exhausting and a public nuisance. I have been on a DO NOT CALL LIST for years and it doesn't help, the Fed doesn't care...just look as who's administration is at the helm and that'll tell you something.

received  call from this guy telling me I had a loan and i had better paid the 4 months back pay.
the original number does not work and the 888 number he gives is a bogus

I guess I blocked this number a year ago. It probably is the HVAC service peddler, I've got a lot of those lately.

You are correct