Changing order

I went to woodmead McDonald’s and I ordered the full SA breakfast with coffee. The hot chocolate option was greyed out and indicated not available on the self service machine. Then after paying I went to the till to find out of really hot chocolate is not available. A lady called Inga told me there is and I asked if I can change my coffee to hot chocolate she said I cannot change. The indicated that apparently at their store people are not allowed to change orders and I must just take what I orderd. I didn’t want to change the whole order just the coffee she said not I cannot. On the SA break menu it indicated that it’s 2 round eggs but what I got was scrambled eggs ibread. I paid for this service and this Inga lady was just plain rude as if I’m buying on credit.