They said they have no idea why I would have an overpayment in other words they don’t know what happened.
Since you did not receive aid at two schools at one time, this does not appear to be the reason.
Were you originally enrolled in at least 12 credits, then dropped to below 12 before the end of drop/add … even if you added a class after the drop/add period ended, the credits won’t be allowed to count for purposes of Pell. If you dropped below 12, your Pell would have had to be adjusted - reduced by 25%. Was this possibly the reason?
Another possibility is that your file was verified and the EFC changed, resulting in a lower Pell payment. If the school didn’t have the new EFC set as the one to use for payment, you might have received too much Pell - they could have caught it later and made the adjustment at that time (again, they have to make the adjustment, even if they find it much later). Or you may have made a change to your FAFSA after they verified it - students do this a lot - allowing the computer system to pay you at the wrong EFC. They may have caught it later and would have had to adjust your payment.
Yet another possibility is that you were not selected for verification, but you made a change to your FAFSA after you received your Pell … the EFC was higher, and your Pell had to be reduced … and the school didn’t catch it until later.
The problem is that financial aid files only have to be held for a set period of time - yours may have been shredded already. In that case, it may not be possible to find out what happened. You would then be stuck paying what you owe, because they say you owe it.
Talk to them, be really nice, and if they say you are stuck paying it, see if they will compromise. They very well may not, but it’s worth a try.