Garmishment over payment question

Automatic garnishments have been taken out of my pay for about a year successfully. I get paid on the last working day of the month.

When my wife changed jobs our income dropped significantly enough to have our lawyer file for a change in income. The judge approved it on 28th Aug which I realize is too soon to affect my Aug garnishment. So when the old garnishment was taken out at the end of Sept as well I called up the Trustee's office. They agreed they had screwed up and not notified my employee. They also said if I wanted to get the over payment back I should contact my attorney. Well he wants $200 to file.

Anyone know what I need to file to get the over payment back. The overpayment is $500 so it's quiet significant - at least for me.

I'd just wait, you'll get the overpayment back eventually.

You would think that would be the case.
But the mistake was made by the trustee in the delay to notify my employer. Once they submitted the paperwork the garnishment was corrected.
There is a form to file to get the over payment back but in searching I can't find the number for it.