when they took over my loans from salliemae they told us (in writing) that auto-pay would transition.... then it didn't transition, and they tried to ding me for a missed payment. what a nightmare. ultimately my issue was resolved, but only after i filed a complaint with a team at the federal student aid office that handles disputes that cannot be resolved through the lender:

https://studentaid.ed.gov/sa/repay-loans/disputes/prepare/co...

then a navient person in that department reached out to me almost immediately.

Edit:

You can also file complaints for general consumer financial help here:

https://www.consumerfinance.gov/complaint/