Refund for overpayment on tuition payment plan

I signed up for a payment plan to split my tuition into monthly payments. When setting it up, I entered the total amount of my tuition without accounting for potential additional financial aid that hadn't been applied yet.

I will have overpaid my tuition if I get the financial aid. Has anyone here gone through the process of getting a refund for an overpayment like this? I think I either have to reach out to Nelnet or One Stop for this issue and wondering how long it took for them to process the refund