I’ve got the knob off by pressing the release on the knob itself but the trim plates will not budge. I thought they would slide off or unscrew once I had the knob off but I can’t budge them. There is a slot ontop of the trim plate on both sides of the door. I don’t want to damage the old knob as I might have to replace it when we move what can I do to remove these plates and get to the retaining screws?