Try this, in your best radio announcer's voice, when answering these spam calls (Don't pause long enough for them to say anything - just keep talking):
"You are caller number 5 on KLUE, the best station in the valley for music, news and talk. You have 3 seconds to answer today's question, starting now. 3 - 2 - 1. Sorry, you didn't answer the question. Better luck next time. Goodbye." Then hang up and block the number.
Or try this:
"9-1-1, what is your emergency?"
I did that once and there was silence for a couple beats, then a man said, "Oh, my God, I am so sorry." Then he hung up. I have never received another call from that particular number.
I received a call from this number, I let it go without answering, but I found it interesting that the only thing it said for location was United States, which it probably was not.