Its a wall unit that need the filters cleaned/changed. The problem is that I cannot get the face plate off, the bottom pulls away from the inner unit but the top will not disconnect. I have pulled the unit partly out of the houseing to try to get the plate off, but still does not want to come loose. I have pounded it from the bottom with as much force I dared use for fear of damaging the plastic cover. Its a GE heat/cooling type, big unit, any suggestions?