Well, you don't have to just take this sitting down. First, there are ways to appeal these decisions through the insurance companies, having your doctor write a letter of "medical necessity". If that doesn't work, then you can turn to your state for help.
Did you know that many states offer assistance in dealing with insurance companies in appealing these types of issues? They do. So if you've been denied coverage for something, go to this website and contact the agency in your state and get help to see if you can win your appeal for coverage.