Unfortunately tax offset lists were submitted to the IRS in early December so your name is already on the list. A letter would have been sent from your guarantor informing you of there intent to garnish in late August....that was the time to act.
Your interest is accruing because you are not paying...you cannot make headway if you ignore it.
Have you looked into consolidating it with the Direct Loan program....you would automatically be assigned to the income contingent repayment plan. All that info is in the sticky section at the top of this forum.