Coverage vs Benefit

Question to the people. My Employer offers Health Insurance and our Enrollment period is in April. Our coverage then takes effect on June 1st.
Our documentation says “Coverage Period: 06/01/2022 – 05/31/2023” but says nothing about Benefit year.
I have scoured our available documentation and cannot find anything stating our Benefit Year is different (or the same).

Should I expect my Benefit and Coverage years to be different schedules if it is not stated somewhere?

My issue now, Health Insurance is trying to say that I was ineligable for a “routine service” which they cover once per year.
I have called and spoken with 4 humans about this. The first said “It should have been covered, we will re-process the claim to get it fixed.”. Second said “It’s been approved, you only owe a co-pay from this other charge on the same EOB.”. Third person said “It wasn’t covered, you need to talk to the Providers Billing Department to understand why it wasn’t covered.” (Cuz that makes total sense??)

Fourth person stated that it is a “routine service” which is covered once per year, and showed me where I can find that online. But the thing she showed was a completely different “routine service” which I did not have performed. The fourth person could not direct me to anywhere where it stated this was a one a year service.