Checking my last day of health coverage - 20 weeks in

I was told my coverage ends on my last day, but the letter says the end of the month. I have read a lot of threads here and could not find my exact situation. The letter is unclear about dental and vision. How did you confirm your end date?

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.