Bad servives

I went to McDonald's Waterkloof. I bought 1Big Macs Meal and 2 Mac Chicken regular. I swiped at the window then on the next window i realise the guy sold me 2 regular meals and 1 medium. This is not the first time the do this to me at the drive through. Its been 10min and im still waiting for the medium meal to be corrected. All the cars behind me have left. I just wonder what are they doing woth my burger.