An Oregon State Employment Garnishment in Oklahoma

I was given paperwork for a wage garnishment from Oregon State employment Dept. (I live/work in Oklahoma), last week. It was for unemployment insurance overpayment in 2006, 3 yrs ago. It appears that a state agency does not have to go through the court system, in order to file a garnishment??? I received copies of the garnishment today, at my home, along with a "Challenge to Garnishment" form, that I am looking for information on how to fill out. In Oklahoma I can file for a "hardship", if I know where to file/paperwork to fill out, etc.... I don't think it should be my fault as they calculated my employment benefits incorrectly, at the beginning, and now want me to pay this immediately, since it was their messup, not mine. Do I file for hardship with the state of Oklahoma or Oregon? By the time I pay utilities, gas to work (105 miles a day r/t x 5), house payment, theirs nothing left to buy food, even though I make ok wages.
Thanks for all your advice..

Have you not been given notice of this before?

State and federal debts do not require a court order.

Just 3 weeks ago, I received initial notification by Oregon calling me in OKlahoma, at work. I signed a wage assignment at this time and faxed it back to them. Then found out that I couldn't realistically give them what I had agreed to . I sent them/and payroll a recend on the wage assignment and they jumped on the garnishment..They also filed with their county in Oregon, a tax lien and added those fees to the initial overpayment. It is now on my credit report.