iphone se 2016 has passcode that lock the phone but we never set one. how do we unlock it

Hello,

It appears you may have a disabled mobile device or forgotten device passcode. Refer to this support article for various methods that you can use to resolve this. Which one you can use depends upon your equipment configuration. --> If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

I understand that you are referring to the passcode that is used to get to the Home Screen of your iPhone. You will have to reset the passcode to your iPhone by following the instructions in this guide published by Apple 👉  If you forgot the passcode or if your iPhone has been disabled. You will need a computer to execute this procedure and all the data on your iPhone will be erased.

Axel F.