It's a system message from Sallie Mae. This is not their collections department, rather usually an automated message regarding account access, system status, system interruptions, etc.

FYI from Sallie Mae about their website being down for a week

Message from Sallie Mae telling me the site will be down for a few days so no transactions.

@Leah Probably because they use an agency to perform the robocall for them.  In my case they left a 23 second blank message, but I am a SMC loan holder so Sallie Mae makes sense.

Even though the message says it's from Sallie Mae, it isn't!!!!!  I verified by checking the Sallie Mae website and calling the number on the website.

Sallie Mae just telling me of a changed due date.

It was Sallie Mae informing of the new payment date.

It's from Sallie Mae's student loan department. They recently changed the payment cycle due date for many of their customers. There is a good chance you do not owe them money, mine was just an FYI call.