offering a settlement on my Navient school loan

I received a settlement offer from National Enterprise Systems offering a settlement on my Navient school loan. I called and they stated that entire Sallie Mae balance so I was gonna settle for $8,500. When speaking to my credit union about a loan they stated that shen is showing two Sallie Mae accounts and the settlement letter from National Enterprise Systems stating original balance of $17. So I called National Enterprise System back and they looked at the credit and said yes, there is two loans. They only have one. My next step was to reach out to Sallie Mae (under my maiden last name: Rebecca Zierk). After being transfered four differnt times I was able to speak to Hannah. She said that the other loan is just “sitting” there since 2009 and has not been assigned and dont know why. That upset me that they are sitting on this loan and not sending me anything about it so this entire time the balance is going up in intereset rate. I found that totally not fair and unacceptable. I asked her what can be done and all she says is to wait 2-3 days for her to complete a research form to have it assigned to a collection agency. I asked if they are going to take money off for not sending me anything in the past 3-4 years, she said I would have to settle with the colleciton agency. Im trying to pay on my school loan, hence why I was going to settle with National Enterprise System, and now to only find out there is another one just sitting there.