I think this is an outbound call number that Sideline uses. Not sure why it shows up versus the caller ID of the person actually calling me. Maybe a bug in their service?
Its clearly Spam
Keeps calling. No one there and leaves no messages.
Not spam. Exchange phone number for the Sideline phone application which allows you to use a second number on your cellphone. I have YouMail for my regular number and this number shows up every time a call comes in through Sideline.