Keeps calling here, we do not answer.

These calls from this number are getting ridiculous. They won't leave a message and I refuse to answer. I get at least 4 calls a day! RIDICULOUS!!

They left a message saying it is Highmark trying to give some valuable information about benefits. Left the toll free number 844-957-6763.

I received the same note as Natalie.  Same message about Highmark wanting to provide valuable info and same callback number at 1-844-258-3428.  I actually dialed that number and it was an automated message about filling out a wellness profile, info on some features on the Highmark website, and getting a flu shot.  Total time was 3 mins 34 seconds.
 FYI, Highmark is a health insurance provider in Western PA.  The 978 area code seems to be in eastern Massachusetts, so Im thinking this is some sort of robo-call service that companies can hire.  

Anthem Blue Cross & Blue Shield. No message left but goes to automated message when called back.