This happened to me and I reset everything
But to finish setting up my phone it still says it needs the old passcode. Of course when I put it in it says it’s incorrect. I don’t know what to do.
iPhone 11 Pro, iOS 15
There is a special process .
You need a computer and the Apple ID password, but unfortunately it will wipe the phone
If you forgot the passcode on your iPhone, or your iPhone is disabled
video
How to re your iPhone if you forgot your passcode - Apple Support