I didn't recognize the number so didn't answer it.  No msg. was left and when I blocked my number and called back, there was a recording saying the number is not a working number and to check the number and try the call again.  It is now blocked!

I got the same thing and even called with my number unblocked and it said its not a working number. And today I received a private call. Whoever it is, it seems sketchy.