Is your Part D a policy through an insurance company?
You should be able to choose a Part D policy, but you need to compare the rates. Check the back section of of your Medicare and You 2017. It or Medicare online lists policies available in your area.
I have used Medicare Advantage for several years instead of Medicare. Most MA plans had $zero deductible and $3 to $6 co-pays for most generic prescriptions.
You may have other options. The ‘enrollment period’ is still open for selecting 2017 plans. Check your Medicare and You 2017.
Deductibles, co-pays, and costs can vary greatly.
Some generics and name brands cost significantly more, even under the approved Part D drug plans.
Correction: Enrollment for 2017 was between October 15 and December 7.