I just chanced to see your JDRF posting today to my question. If seems I now will have to pay more than $0 for my copay. (I never had Part D or a supplemental policy). I do not know whether my original arrangement with the same pharmacy - not Walgreen’s - for all those 10 years was made in error in my favor or Medicare’s policy has changed. If I find out I will make another posting here.
My new pharmacy (Walgreen’s) went through their current instructions from Medicare and assured me my copay will be much less than 20% of Humalog’s list price. I have not purchased insulin from Walgreen’s and will post my cost when I do.
Page 37 in the 2019 Medicare Handbook talks about a copay for my case at least.
Re your other issue I deal with 1st party providers only, in my case Medtronic, Dexcom and Walgreen’s. I find most 3rd parties to be problematic at best.