On Wednesday, the Consumer Financial Protection Bureau (CFPB) filed a lawsuit against Navient, the largest student loan servicer in the country. If you have a student loan, there is a good chance that it may be serviced by Navient. Navient, which spun off from Sallie Mae, has more than 12 million customers and services more than $300 billion of government and private student loans. Here is what you need to know and the action that you can take …