every few months this number calls and rings twice then hangs up.. for two or three days in a row then stops...when you call it back nothing happens

For the last several weeks I get every day almost a call from this number.
When I pick up, no one is on the phone at the other end.
I tried to call back, but the message says that the voice mail box is full, 'please hang up'
I wish there was a way to just block them forever.