I have been receiving calls from this number, they began calling me at work. It is not Sallie Mae, it belongs to a company called AIS. They are a collection agency that buys debts. They purchsed a debt from a lender that I had paid for less than the full balance. ($480 on $640 balance) I paid the settlement amount to the original lender. They bought it in full for 640 and now keep coming after me and won't accept the paid in full letter from the original vendor for proof the balance was paid.

Be careful of these people, they are rude and will not give up. I am waiting for them to take me to court so I can counter-sue them.