Wrong Order

I went to McDonald's Westgate Mall and order a DOUBLE BIG MAC which costs R60.00. And I PAID that much. I got my order (Take away) and left. When I got home I open the burger and it's the normal Big Mac, NOT the one I paid for, which I believe is less in price than what I paid. So I paid more for a normal Big Mac? I am honestly disappointed with this and pretty ****ed off