Medicare Parts A and B are sometimes called "Original Medicare." Original Medicare allows you the freedom to see any doctor who accepts Medicare. Most do. It’s not like an HMO, where you can see only doctors in the plan’s network.
Many people get signed up for Medicare Part B automatically. If you do not want it, you must opt out. Otherwise, the money is automatically taken out your Social Security payments. You should get instructions on how to do this when you are first mailed your Medicare packet.
Some people opt out of Medicare Part B because they still have coverage through union or employer health insurance. As long as your coverage is considered “creditable” you will not pay a penalty for signing up late. Talk to the group benefits administrator of your plan before opting out of Part B. If your coverage does not meet this criteria, or you have no other coverage, you may pay a lifetime penalty if you sign up later for Part B.
If you have traditional Medicare, make sure your doctor "accepts assignment" before you make an appointment. Medicare decides what it will pay for any particular medical service. This is called the Medicare-approved amount. If your doctor is willing to accept what Medicare pays and won't charge you any more, he or she is said to "accept assignment." But if your health care provider charges more than Medicare pays, you will have to pay the difference.
For more information about Medicare Part B, see the Medicare web site at www.medicare.gov or call 1-800-MEDICARE.