This is a service company that does mass broadcasts of messages via phone, text and email. My employer uses them to stay in touch with staff in the event of an emergency. They ran a test last Saturday and the caller ID was 877-316-8308.

I dont know who this is

I don't want to be contacted by these people, it is some kind of credit card debit relief. They never leave the name and sometimes they offer a "remove from list" but it does not work. This is harrasment, I have signed up for Texas No Call but this has no effect.

This is the Emergency Alert and Response System for government employees.  If you got a call from this, there was either an emergency or a drill (more likely) and government employees were called to check in with their respective division.  (I added this information because of Joe's comment--it's not just Army)

If you are not a government employee, your phone number got accidentally added to the database.  If you can't call the number back to be removed, I'm really not sure what you can do, but the system is called EARS - Emergency Alert and Response System.  

This is a Headquarters Department of the Army Alert Notification Number.

Who is it?  Won't answer until you leave a message.