I asked student loan Navient to provide me with proof the student loan is mine.
They sent a list of loans, but the signature page was not mine. It was someone else name, address, social security number. I mean all of there personal information.
What should be my next step?
You have two choices.
You can bring this issue to their attention yourself and ask them to provide you with the correct documentation.
Or you could find an attorney licensed in your state to contact them on your behalf. Paying for legal representation in matters that might involve a legal complication, is a good investment.
Just by itself, I’m not sure the disclosure of someone else’s information gives you any leverage. Now if they disclose your information to someone else, that’s a different story.