Not only Mayo does not take Medicare Advantage plans (except for a few situations in MN) but Medicare Advantage plans are constantly being dropped by other providers across the United States.
Unfortunately, the insurance companies advertise incessantly on TV about Advantage plans
"getting all your benefits" without telling people the real truth - YOU LOSE CHOICE! You have to go to their doctors or pay $$$. They deny coverage frequently because that is their business model to increase profits by not providing services. There are many complaints against Advantage plans, and people should call their Representative in Congress about it.
AND once you are in an Advantage plan, and you want to go back to Original Medicare so that you can go to the doctors you want, yes you can go back to Original Medicare BUT to purchase the Medigap insurance plan to cover the 20% that Medicare does not cover, you are in trouble. Insurance companies no longer have to accept you, or they can charge you a higher premium than you would have paid in the beginning.