Checking my last day of health coverage - any advice?

I was told my coverage ends on my last day, but the letter says the end of the month. I have been trying to stay organised about it. I do not want to be surprised by a bill. What should I do about appointments?

Keep everything in writing and save the confirmation numbers. It made the follow-up calls so much easier.

Dental and vision sometimes end on a different date from medical. Mine did.