Navient Debt Collection Complaint

Navient Debt collection department,

Federal student loan Taking/threatening an illegal action Threatened arrest/jail if do not pay Florida

I am writing on behalf of my - year old -. She is paying on her grandson 's - - - loan, however they call her day and night requesting that she pay it off in full or they demand a very large payment. They threaten her with foreclosure and lawsuits. She pays monthly and they still call, they even call her on holidays. She asks them to stop calling and has put it in writing and the harassing calls continue. They 've told her they 'll call when ever they want and will continue until she pays off the loan. These calls are making her - and I need to know what we can do to stop this harassment?