Who called from 4253668920

Listed as "NA" in caller id.  Don't know who this is but call from 425-366-8920 left no message.  I see one other person recently received same sort of call so am including my comment.

Same, listened for half a minute and hung up.

Caller id  "CSB" called ; 9/30/16 4:03pm & 9/29/16 2:50pm; no message. When I call the number I get a normal busy tone.  Suspect its political survey call.