When Beverly Dunn called her new primary care doctor’s office last November to schedule an annual checkup, she assumed her Medicare coverage would pick up most of the tab. The appointment seemed like a routine physical, and she was pleased that the doctor spent a lot of time with her. Until she got the bill: $400. Dunn, 69, called the doctor’s office assuming there was a billing error. But it was no mistake, she was told. Medicare does not...