Product: Student loan

On Saturday, XX/XX/XXXX, I received a delinquency notice by mail from ACS, the lender 's servicing agent, dated XX/XX/XXXX. I was very surprised as I thought I had made a payment in XX/XX/XXXX and, moreover, the account should have been pre-paid for a period of at least a year, if not two. I had the same issue 10 or more years ago, the servicing agent acknowledged back then the account was pre-paid ( by approximately 4 months ) and I have been paying it further in advance ever since. I checked my bank records and saw no check or ACH payment in XX/XX/XXXX and immediately scheduled a {$600.00} payment. Because it was a Saturday, the earliest the payment could be scheduled by ACH was Monday, XX/XX/XXXX. After scheduling the payment, I used the " contact us '' feature on the ACS website asking for confirmation of the pre-paid status, confirmation that no late fee had been applied, and for the date through which the loan was pre-paid. On XX/XX/XXXX, I received an unsecure email from ACS advising that my account was " no longer eligible for the special benefits of the incentive program '' due to the alleged delinquency. I was unclear as to what " special incentives '' applied to my account, but upon checking the ACS website I noticed they had increased my interest rate from 3.125 % fixed to 4.125 %. On XX/XX/XXXX, I received a secure email, which I was finally able to access with great difficulty. The email very curtly stated my account was not pre-paid and that I HAD been assessed a late fee ( the email stated due to a missed payment due XX/XX/XXXX which apparently meant to say XX/XX/XXXX ). I contacted customer service and while the representative hedged considerably about how far in advance the account had been pre-paid, she did understand that I had been paying in excess of the installment amount for years and said their processing department would review and have someone contact me. The representative also indicated that while a late payment had been applied it had been reversed. I received a statement dated XX/XX/XXXX, which indicated, with the {$600.00} payment mentioned above, the account WAS pre-paid with the next regular payment due XX/XX/XXXX. The {$600.00} payment mentioned above would have advanced the next payment due by no more than 3 months, meaning that as of the time of the alleged " missed '' XX/XX/XXXX payment, no payment was actually due until XX/XX/XXXX ( i.e., the alleged " missed '' payment was made more than 2 years in advance ). The same statement indicated {$6.00} of my XX/XX/XXXX payment had been applied to a late fee. I can not locate a copy of the promissory note, but I is my understanding that pursuant to Federal law and the terms of the Note that excess payment amounts are to be applied to future installments unless the lender is notified otherwise. I have not ever indicated to the lender or its servicing agent to apply excess payments in any other fashion. I attempted to contact customer service at ACS over 3 weeks ago. It was quite late and I was surprised to reach anyone, but I did speak with a representative and described the issue and asked to speak with a supervisor. The representative indicated that no supervisor was available due to the late hour but took my cell number and said someone would contact me. To date, I have heard nothing, by phone or mail or email, the website still reflects the higher rate of interest and I do not see any indication that the late fee was actually ever credited. Copies are attached of the XX/XX/XXXX statement/notice, XX/XX/XXXX statement, unsecured emails regarding the XX/XX/XXXX ACH payment and loss of incentive benefits, payment history from the ACS website and the secure email.