It is confusing. Suzy's had her medicare for a year and I'm still stumped.
What you should do is call Humana insurance about either a supplement plan or an Advantage plan. But do not commit to a plan with them until you gather as much info as possible such as what other insurance companies can play ball in your area. Also you should call your local government and get to the bottom of what exactly are you able to acquire at what cost. And do not wait.

When Suzy was approved, I recall she had medicare A, B and D. I called AARP and they told me she can not get a supplement plan because she is not a retiree. As it turns out AARP doesn't offer those kinds of plans to those on SSDI, others do however. I did pick up through AARP a Enhanced drug plan for Suzy. Since then, this past open enrollment period, I switched her to an Humana PPO Advantage plan with the drug plan built in, all at a cheaper premium. However, I wanted to get her a Supplemental Plan in which I believe is much better but was told by a few that in my area of NOVA those plans are not available. This I'm still looking into to make sure this is true because it seems many doctors are now dumping those on medicare in which only those doctors who except medicare are the only ones where Suzy can use her Humana Advantage plan, but if I'm not mistaking a supplement plan many more doctors except because medicare is not a requirement (I think)

Confusing as hell!