I Phone 8 - "Password expired" pop-ups

I continuously receive "passcode expired" pop-ups. "Passcode expired. Your I phone unlock password has expired. Change Passcode." I have downloaded the latest software update, and re-started my phone numerous times, but I cannot get this to go away. So, I cannot use my I Phone (8). I have followed the directions on a number of websites. I cannot make a call as this is my phone and I can't access it. Please help?