Everybody knows "Do Not Call" does NOT Work. Try "No More Robot Calls" @ WWW.nomorobo.com. It's a no fee service (for VoiP land lines), eliminated 95 % of my Spam. Check the site . . . it explains how it works and it costs nothing (for land lines) ! [And No, I don't have stock in the company, but I wish I did!]
This is Navient calling to collect or remind you about your student loan payments; they took over Sallie Mae's old accounts so if you've never heard of "Navient" that may be why.