Checking my last day of health coverage after 18 years as a dental hygienist

I was told my coverage ends on my last day, but the letter says the end of the month. I worked as a dental hygienist before this. I have an appointment next week. Did coverage match what HR said?

Thanks for writing this out. I went through something close to it 14 months ago, and it got easier once I kept a simple log of every call and form.