That might not be actually an option. Well the provider can do it for free, probably; but they may not be able to accept money for care that was denied coverage. A Medicare provider can charge patients for things outside the scope of Medicare, but generally can't charge for things in scope but deemed not medically necessary: ex if Medicare says 6 PT visits for whatever and you would like to have 8, you can't pay the provider for two more; you'd have to find a non medicare provider or come back with a fake moustache.