have been customer of Navient

I have been customer of Navient as far back as 2004, and have made best efforts to pay back a substanstial student loan (private loans – my federal loans are in forebearance and due to be repaid in Feb 2013). Recently, they have placed me in collections with a ruthless collection agency, National Enterprise System, or “NES”). Sallie has never sent me notice that I could not send them payments anymore, that payments must be sent to this collection agency only, and the agency began a series of about 15 phone calls a day before I received their own written notice that I had to repay to them about $30,000 worth of student loan debt. Sallie Mae, in fact, directly accepted an online payment made on the Sallie Mae website as recently as 11/19/12, a few days after the harassing calls from NES, and also send me an email confirmation regarding receipt. On 11/27/12, I spoke with an NES representative and told them I have made a payment to Sallie Mae, and the rep told me they had no record of this payment, and that I must only send payments to NES. I contacted Sallie Mae on 11/28/12 at approximately 10:30 AM EST, and the Sallie rep told me that, while they accepted my payment and posted to my account, they would not accept payments from me. I asked that, if that was the case, to refund the money to me so that I can forward the payment to NES, and they refused. I asked how they could accept this payment, and not notify NES of the transaction? I asked Sallie if my debt was sold to this agency, and the rep said no, the agency is working on behalf of Sallie Mae. I asked how could that be if both agencies are not communicating in regards to payment? I was then told by Sallie if I refused to work with collections, collections would begin the process of wage garnishment, which is a violation of FDCPA law. At best, I am default of $1011.17, but, if allowed, I can make this up. Sallie Mae also continues to send me email notices on repayment options. Why do that if they are refusing accepting payments?