I paid the "balance due" online thinking my 2 stud...

I paid the "balance due" online thinking my 2 student loans were paid off. 3 months later UHEAA reported me for delinquent on my 2 loans for $3. They never contacted me one time before they reporting to the credit bureaus for 3 bucks. When I called them to ask where the $3 balance came from they told they were "fees unpaid" and that I should file a dispute with the credit bureaus.