do not know who this is, so we don't answer

I have received 2-3 calls every day from this number. On caller ID it shows "unknown number" and the first couple of times I have answered nothing was said.  I have no idea of who they are nor why they would be calling. I am on every do not call list and I still get these stupid calls, so the do not call list is just a big joke.

770-932-5865--local to the Atlanta, Georgia area
unknown caller

They don't leave a message, so I don't answer and I block