Ok I just went through this myself. First things first.
1. Perform a Privacy Act Request through "U.S. Department of Education" requesting "All student loan account information".
2. On the same day write a debt validation letter to the collection agency. If you don't know who that is, ask the Employer for a copy of the Garnishment Order, it should have the name of the creditor AND the collector.
The debt validation should include specific terms: Oregon has specific debtors rights. Google "Debt validation letter Student Loans" SEND IT CERTIFIED MAIL - Electronic return receipt.
3. Next write to the Financial Student Aid Ombudsman. Let them know your Borrowers rights have been infringed on. Google "FSA Student loan collection rights" there is a list on FSA's site that explains your rights. List out Verbatim the rights you feel were violated.
4. Copy and paste that letter (minus the address for the Ombudsman) and direct the same letter to the collection agency.
All correspondence to FSA and the collection Agency must be certified. This is proof you sent the letter. ALSO make sure you put in your correct address. "All correspondence will only be received by U.S. Mail at the following Address"
Do not communicate by phone. (Yet)
Unfortunately from there its a waiting game. Oregon has Validation time requirements look them up. If the collection agency doesn't respond timely, start filing complaints to the following:
Consumer Financial Protection Bureau (did wonders for me) and easy!
Better Business Bureau
Oregon Attorney General.
The big thing here is you need to know what your state a federal rights are READ READ READ. Learn the FDCPA and call them out if they break the law. Log everything.
Just so you know (but no guarantees) this happened to me and I went through the process I just lined out... Department of Ed issued refund checks for my garnishments...in full. BUT if you owe just know you will have to pay.

