The bill holder should contact the U.S. Treasury Debt Management Center toll free at 1 (888) 826-3127.
Also see: https://www.fiscal.treasury.gov/dms/faqs/for-the-general-public.html
The BIA cannot provide payoff balance information on debts that have been referred to the U.S. Treasury. Irrigation project staff may communicate the origin of the debt such as: the original amount, why the bill was created, and why it is valid to authorized parties only. Third parties must have written authorization from the original bill holder to speak with the U.S. Treasury about another person’s irrigation bill.