Pathetic service....rude manageress!!!

I went to McDonals in Parklands last night and had the worst experience. I ordered 2x Big Mac Meals and they only gave me one burger. When I went back to inform them of this, they told me they gave me both burgers. I told them this was wrong and insisted they check CCTV. Both the lady who served me and the Manageress told me they refuse to look at CCTV and refuse to assist me further. The manageress was quite rude to me. I quickly went back to my car and then she asked the security guard to lock the door so I couldnt go back in. Pathetic service. Ill never go back there.