Called and hung up without a word.

Same.  Hung up, no one there

I got a call from this number on my DNC landline while I was outside. Since the number was close to a friend's number, I called it right back. I got a message saying the number I was calling is not a working number. This number will be blocked.

Same as above, they called, no sound at all on the line, and then hung up

2 calls from this number answered but no one there.