Product: Student loan

My federal student loan servicer is Navient. I have had issues with my extra payments to individual loans that were extremely unfair to me. I was troubled that my loans with the highest interest rates had balances that were not going down at all when I first started making payments. I asked Navient about this, and they assured me that my payments were being allocated in the most efficient way, as calculated by them. I accepted this answer but was still troubled by it. I decided that I would start to make extra payments to one of these accounts. This would not be something that I would do every month, but when I had a few dollars left over at the end of the month.
I made a few payments to one of my unsubsidized loans that had a principal balance that was not going down. I made my first extra payment of {$50.00} on XXXX/XXXX/XXXX to a specific loan and then made another extra payment of {$30.00} on XXXX/XXXX/XXXX to that same loan. I distinctly remember checking a box when I made these payments stating that I intend to make my next scheduled payment and that I do not want my due date pushed out more than one month. I assumed that my auto payments from then on would be allocated properly. I was wrong. At the time, as I was in a financial situation where I could not make more extra payments, I continued to make my automatic payment every month but did not pay attention to my account otherwise.
Later on I logged into my account and went back to look at my statements and realized that my due date was pushed out due to my extra payments. for the next three months {$0.00} was allocated to the principle on that loan. ( Screenshot of balance showing {$0.00} going to principle from payments is attached ). 

To my own fault, it took me a year to notice this issue. I reached out to Navient and was told that they were unable to correct the issue. I still feel that this is wrong and should be correctable. ( I do not have documentation of this message as Navient only stores documents on their site for 12 months ).
I have been making new extra payments to one of my Navient managed federal student loans and I feel that the way that they are handling extra payments is fraudulent. I continue to struggle with payments being misallocated. They still have a box where payment preference can be selected ( screenshot is attached to this complaint ), but I feel that this box is completely ignored. Due dates are still always advanced and the next auto payment allocated to the account is often a meaningless amount of a few dollars or less, which is not even enough to cover the outstanding interest on the account. 

Navient has corrected this overtime that I have noticed the issue right away, but it is often like pulling teeth. I have to send an email to Navient each time that I make an extra payment demanding that my account balance be reset right away. Sometimes this is heeded without issue, sometimes it is ignored, sometimes I receive an ignorant response about not being able to complete my request and I have to send more correspondence to get this done. I have been told by a rep that all future payments would be handled properly. The next payment was not and the next rep told me that their system does not allow for them to make note of how all extra payments should be applied. They have truly given me the runaround on this issue and I honestly feel that they are not as incompetent as they act like they have and that this is a fraudulent attempt to extend the life of my loans. 

I know that {$80.00} in extra payments is not a large amount of money. If it had not been just about the {$80.00}, this may not be an issue. I honestly feel that Navient is actively trying to defraud me with the way they continue to handle payments. They got away with {$80.00} worth of my payments, and I imagine that I am not alone. I am filing this request in the attempt that it can help someone else who has been hurt more than me. 

I did not realize that I could file a complaint about this until now, otherwise, I would have done so.