Sallie Mae Navient I don't owe you anything. Nationwide

I took out a student loan for my daughter's education way back in 2000 or 2001. As far as I knew, it was paid off in full, probably in 2010. However, 16-18 months after I had paid it off in full, and had not heard anything differently, I got a letter from Sallie Mae, who inherited Student loans from Citibank. They said I still owed $1034, and two hundred and some dollars in interest. However, I never heard or gotten one correspondence to this effect for at least 16 months. They called me and called me, and I tried to talk with Sallie Mae, telling them why I did not owe them any money. However, the harassment continued until I paid the $1034, but I told them I would not pay interest on something, I was not aware I owed. Had I gotten something from Citibank saying I still owed money and some type of payment precedure, I would have continued to pay it off. I never missed a payment previously. Citibank, sold their student loans to Sallie Mae, then Sallie Mae, placed all their student loans into something called Navient. When I would not pay the interest, they sent it on to a collection agency called Pioneer something. I called the student loan federal program and sent all the information I had to Federal student Aid. PO Box 84, Washington DC. that was on May 27th 2015. I never heard back from them, so figured the problem was taken care of until Delta Management a*s. inc. Chelsea MA, sent me another collection letter, as well as a couple of phone calls. I am sending them back a letter, saying I am not paying this. Why would I pay interest on something that no one told me about. It is now $3o6.97. I am still not going to pay this. Sallie Mae can not possibly go bankrupt because I don't pay this. No one has ever sent a copy of my school loan showing that I even owed the $1034. I paid it because they weren't only harassing me, they made phone calls all the time to some of my family and even my friends. I don't know how they got any of their phone numbers, but they did. This is not right. I should not be harassed in my older age by these people. This is just plain sick.