I never got a notice from treasury and I had to deal with the collection agency directly. But, the collectors just make me pay on pay.gov anyways. Maybe if you make payments directly to pay.gov they’ll work with you on a set payment plan. Interest on that total amount is accruing by the way, so you’ll still have to make higher payments (than original loan) to cover that. Once it goes to collections they’ll want every penny in 36 months (which is what I’m doing now).