I paid off a XXXX XXXX student loan in 2008. I was not aware that an additional interest charge had been posted until some years later when I was contacted by Allied Interstate LLC who stated I owed {$300.00} ( the amount I had paid off was around {$600.00} ). Sometime in XXXX of this year I received a letter dated XXXX XXXX, 2015 that offered a settlement amount of {$45.00} if it was paid within 40 days of the date of the letter. I mailed a check to them on XXXX XXXX which they cashed on XXXX XXXX. That same day Allied Interstate LLC sent me another notice stating that I was still to pay the remaining balance and no mention of the settlement that was offered in the XXXX XXXX letter. They are refusing to uphold the terms of the settlement that they offered of their own free will and accord.