How do I reset forgotten Screen Time password on iPhone?

So I don’t have a screen time password on my child’s phone but I used to but the phone thinks we still do, so every time we try to change the password we can’t because there is no password but there is still a password when I try to use a app “over the time limit” when there is no limit and the screen time password we can’t remember

[Re-Titled by Moderator]