I answered the phone and heard silence. After a couple of seconds, I was connected to someone with massively populated call-room background noise. He was rude and asked for "Michael"; I told him there was no one here by that name and that he had called the wrong number. Then he hung up on me. I assumed it was a debt collector, which was why I told him it was a wrong number. Blocked.
Called them back out of curiosity and hiding my number and true IP. Recording said Thanks for calling back. If you'd like to be placed on our do-not-call list .... Allow 48 hours to take effect.
In such a situation the only button to press is the Block button - no other.