I let it ring a few times and picked up the person hung up. I called the number back and ostensibly it's currently out of service.

I answered when they called me, I had gotten on-line and checked out on-line college courses and they have relentlessly called me wanting to know when I can register for classes etc

the person calling doesn't leave messages, won't answer... or if they do answer won't acknowledge the other person they are calling.....they call at all hours.....