As you need to enter your code before you can change the code over, if you don't know the code, then you're stuffed (technical term) so you'd need to reset the panel by switching it off, undoing it, and putting a jumper across a couple of terminals, applying power, then changing everything back. For this, you need the engineers manual, and as you don't have one, or you may not be competant eniough to do it, as acorn suggest, get someone in that knows how to do it for you.
Mike T, January 2012
