s.o.s. i don't answer and they don't leave a message

Received numerous calls from this number over the past week or more.  No messages left.  Comes up Processing on caller id.  Very annoying and harassing.  Am on do not call registry.  I am getting to the point where I am going to notify all the proper authorities to stop this harassment.  Had enough.

Did not answer;  no voice mail left.

Phone call at 12:20 EST.  Nobody there, I hung up

What is the goal of these calls? I'm sure no good.