We get these robo calls at all hours of the day and night, sometimes in the middle of the night. A female voice starts to tell us we have won some vacation package. The caller I.D. shows Boise, Idaho, as the caller. I have gotten this exact same call from other numbers and they are scams.
I called it back and got an auto message saying "the survey your calling about has concluded, to be removed from our list, press 9". I did so, and waited a couple seconds and got a confirmation of being removed. Not sure it is works, but hopefully!