Medicare-AT&T Enrollment Process

You should be able to enroll online.  Check out the MEDICARE.GOV website for guidance.

A Medicare Advantage Plan (like an HMO or PPO) is another Medicare health plan choice you may have as part of Medicare. Medicare Advantage Plans, sometimes called “Part C” or “MA Plans,” are offered by private companies approved by Medicare.

If you join a Medicare Advantage Plan, the plan will provide all of your Part A (Hospital Insurance) and Part B (Medical Insurance) coverage. Medicare Advantage Plans may offer extra coverage, such as vision, hearing, dental, and/or health and wellness programs. Most include Medicare prescription drug coverage (Part D).

Don't know for AT&T's advantage plan. But for anyone else who stumbles on this thread, if you're retired Military you need Medicare Part A and Part B in order to get your Tricare For Life. (Mentioning as I every so often see questions from Veterans which may include Military retirees).

Both: Page 13 of plan guide states in part. You must be entitled to Medicare Part A and enrolled in Medicare Part B to enroll in these plans. You should really direct your questions to United Health Care.