Checking my last day of health coverage after 16 years as a software tester

I was told my coverage ends on my last day, but the letter says the end of the month. There are 16 people counting on me, so I am trying to be careful. The letter is unclear about dental and vision. Did coverage match what HR said?

Thanks for writing this out. I went through something close to it 8 months ago, and it settled down once I kept a simple log of every call and form.