This number keeps calling, doesn't leave message.  Outreach Association on caller ID.

Call from that number comes in once a day.  Called it back today and got a recording that they were a share group, making calls for numerous charitable organizations.  If you got a call from this number it was because they were calling for a charitable organization that you had donated to before, at one time or another.

I also got calls from 412-773-8556, 412-773-8558, and 412-773-8559.