It is *not* explicitly illegal to use automation with cell phones, they must have your consent in order to do so however. They obtain it a number of ways, such as adding a statement on a form that by providing your cell number you are also giving your consent. And I'm sorry, but you need to do research before posting inaccuracies. Navient and other student loan servicers do not fit the definition of a "debt collector" by law (since the loans are not in default) and generally do not fall under the FDCPA. And most of the time, they are required by the Department and Federal Student Aid to attempt to contact you a certain amount of times. Sure, payments are best case scenario, but there are multiple plans and even deferment/forbearance options to prevent further delinquency and default. They're not just calling you to get your money, because in most cases you don't owe the debt to them anyway, you owe it to the government or a bank.

In short, they're following the instructions of their employer, the DOE, to do what they do, and it's actually not illegal. Here's an idea. Pay your student loans or make arrangements with them. If you do, guess what? The "harrassing" calls will stop.