I have "Wellpoint" thru my employer, state government
Wellpoint is a subsidiary of Elevance (Blue Cross).
As long as you are classified as a FT employee, Wellpoint is primary, Medicare Part A is secondary.
If a covered participant is admitted as an inpatient to a hospital, Wellpoint pays first, Medicare Part A (may) pay a portion of any remaining balance.
You don't determine when/if to use Part A, the provider(s) handle that.