Whenever the government uses the word “allowed”, be afraid, be very afraid. At that point, the authority is no longer “We the People”, it is “they, the government”.
You're *allowed* to keep your doctor when you're in Medicare as well ... so long as that doctor will accept assignment. Physicians who do not want to have their reasonable fee-for-service slashed, requiring them to make up the difference with non-Medicare patients, or those who refuse to go along with the gubmint having access to confidential patient records by virtue of their insurance coverage being provided by the gubmint simply opt out of assignment, they will not take Medicare patients. Those folks were not necessarily *disallowed* by law/definition, but due to gubmint inserting itself into the system, they surely LOST the care of those physicians.
I say this realizing that when the whole deal is under the gubmint umbrella, either a physician accepts the terms of the system or he doesn't hang a shingle. I'm speaking to the lie right now as things exist ... America needs to wake up and realize it won't be getting any better should we go single-payer or socialized medicine.