Firstly, since the loan was in the name of a parent, your wages should not be garnished. To resolve a dispute like this, you can start by contacting the federal student aid Ombudsman's office
. This office should help resolve any issues or disputes regarding your student loans. You can also submit a complaint at the Consumer Financial Protection Bureau here: https://help.consumerfinance.gov/app/studentloan/ask
Hopefully the Ombudman's office will be able to resolve this for you, or at least provide you with the correct contacts.