They called again - their call was blocked before they dialed my number.

Do Not Call!

Don't you know?
By pressing ANY number, you are only confirming that the number they called is still sellable. I simply just don't answer the phone anymore...

Most excellent suggestion Mr. Fat Freddy. You are a natural and I will pass your "scam" on and you never know, it might work if enough folks pull the same thing.  This is what I do when called for surveys.  I tell them they are taking up my time and time is money and I am tired of giving my opinions free, so now I am charging x number of dollars for any surveys that are ignored anyway.  If they really want answers they will pay, right? Well like you said, "it doesn't seem to be effective, but it is fun"!  Bless you for your humor!

Yet another annoying robo calling scam. Blacklisted number.