Won't answer and when called back it says unable to complete your call. Another bottom feeder?

This number popped up on my phone but attached to one of my contacts so I answered thinking it was someone else. However it was not it was a man on the other end that refused to identify themselves so I hung up now they keep calling to the point of harassment

I answered a call from this number and the person on the other end would only provide his name and would not tell me where he was calling from. The one I spoke with that seemed he was using something to distort his voice. He said his name was Vishnu. This number is now on reject call list.