We have been receiving calls at my work from (415) 691-6526 (caller ID says College Center). For the past month I've been answering and identifying myself and the caller hangs up. I tried calling back and it went straight to the recording that all operators were busy.
Yesterday I simply answered "hello" and the caller asked for my old boss. I asked to be taken off the list and they hung up on me. Today they asked for my new boss. I asked again to be taken off the list and the guy said "have a nice day" and hung up.