Parent student loan

What to do about Navient??? Original loan 26000 25000has been pd. Still owe 25000. Have pd by direct deposit. Recently acct compromised.Had to open new acct. Apparently one bill not pd.Navient notified of new acct, They are harassing us for 224 payment. Check sent Dec1 for undo bill Claim they did not get Also called them Dec 7 Saud the were charging debit card don’t know what they mean as they have new acct no.Plz help want to dissNavient Need help Daughter finished school but has had serious health issues inc breast cancer and hypothyroid surgeries. Income comprises because of health