Navient Solutions, Inc. Student Loan Complaint

Navient Solutions, Inc. Student loan department,

Non-federal student loan Dealing with my lender or servicer Don't agree with fees charged Pennsylvania

I am in a loan repayment program with the national institutes of health and I entered into repayment for my private student loans from Navient and they charged me fees of $1100.00, $1100.00, and $1600.00. I called and was told this is because the loans are now in the repayment stage. This is absolutely unacceptable. So because I am paying the loans I am assessed a fee? How is this acceptable. I was told to write a letter to them regarding this as this was my only course of action. How are we also penalized for paying our loans? This should be outlawed.