Representatives from Navient refused

I have been attempting to pay off part of my student in an amount over $50k. Representatives from Navient refused to provide me with a clear payoff amount that I can easily pay. Instead they refer me to the website which I used in order to make a “future pay[ment]” in the exact amount of the loan listed on the site as my total due. I entered this amount on 12/3/12 on the site and the amount was to be drawn from my checking account on 12/5/12. I chose this date so that I could call Sallie Mae on 12/4/12 to confirm that the amount would be put towards that particular loan, which was my highest interest loan, rather than my other two loans which were of lower interest. Unfortunately, the woman I spoke to, Karen (ID# c36007), told me that I’d also be responsible for interest accumulating on 12/4/12, which would have to be payed in the future. She also stated that since I indicated that I’d like the payment withdrawn on 12/5/12 then no more interest would accumulate beyond 12/5/12. Clearly it would have been cheaper and more convenient for me to have been given a payoff amount that I could easily pay off. This was not to be as you will see. On 12/5/12 I checked both my bank account and Sallie Mae accounts and realized that the payoff had not been processed. When I called Sallie Mae at around 1500 on 12/5/12 I spoke to Darren (ID# c47053) who told me that, in fact, my payment would not be processed on 12/5/12 but instead within 2-4 days and that I’d continue accumulating interest which would also have to be payed. With things accumulating in this way and a payoff amount not made easily available, either through the website or on the phone, it is easy to see how Sallie Mae can milk a few more dollars from me in spite of my good faith efforts to pay off my loan. To add insult to injury, Sallie Mae did somehow miraculously manage to withdraw from my account on 12/5/12, instead of the payoff amount that I’d asked for, two payments each for 2 separate loans in an amount totaling over $1000. These two loans total over $100k and the payments for which are usually withdrawn on the 23rd of each month. Why they decided to do this is beyond me but it certainly is clear that they can process payments quickly when they have a desire to. My only desire is to payoff my highest interest loan at this time without paying extra fees or undeserved interest and somehow this is not possible with this company. They are making deliberate efforts to make this process inordinately difficult and squeeze out every dime they can from me. If no payoff amount is made available to me then how can I not be subjected to these unethical practices?