The stories are harrowing. In complaints to the federal government, retirees describe the costly errors in medical billing that they struggle, often unsuccessfully, to straighten out. One low-income person was told, during his cancer treatments, that they weren’t covered when in fact the hospital wasn’t processing his Medicaid coverage. Another retiree submitted letters to a specialist’s office over a two-year period explaining – with supporting insurance documents – why he didn’t owe the doctor the money he’d been billed for a test. Someone else, while being whisked to the hospital in an ambulance, provided his Medicare and supplemental insurance cards during the ride. He never got a bill – just a call from a debt collection agency. Finally, one retir…