Cashiers attitude and clueless

Went to local mc Donald’s with my sister was so disappointed by the bad service.we redeemed 2 deals from the app using points but was only given 1 deal . I was informed that the other was did not go through . After showing the the history on the app and that the points were dedicated from my points . The cashier along with some lady not sure if it’s the manager on duty disrespectful responded and say they don’t know I must take up with head office because deals are their thing. So my question is why does head office provide service that their in store people have no idea about . I left with 1 meal instead of 2 so who was supposed to eat or not. I’m so hurt by the attitude and the response given by the cashier and yhe other lady . Worse fail me so disappoint. As I’m sitting here 10 000 points were dedicated whilst I only got a deal for 5000 .the cashier name is Tebogo mokoena . I mean if she doesn’t know who must know ?? Me??? I have taken pick of receipt recieved and my points history as reference