I agree. They can say they are Sallie Mae if they are a collection agency trying to pick up the debt. This is usually the case, and I personally wouldn't be giving my info out to some trashy collection agency! If you ARE having financial issues then call them using their official number. If nothing else at least you are keeping them in the loop and sometimes they can even suggest options to help you out.
It is Sallie Mae. I received a call from them at my office. (They apparently were looking for my predecessor who had the same work phone number.) I called them up and they asked me for my account number and or SSN number. I said I was not inclined to give them my number, because I had not initiated the call, nor was I aware of any account number with Sallie Mae. They then asked me to give them the phone number that was dialed, I gave them my work number, and they in turn looked up the account through that. They asked my if I was John Doe, and I knew it was my predecessor.
If you don't have any business with them and they still continue to call, take five minutes and ask who they are looking for. It stopped all of the calls to my office.