It can be changed in theory. There are many products such as corn cob and corn salad that need to be made, and it will definitely take time to make them. If you are in a hurry to take it away, I can exchange it for you. There was corn, but you wanted to change it to something else, such as corn salad. The waiter can't do it for you because it's just in the rush hour. If ps wants to change meals, the waiter in the management group (wearing a blue shirt) has no authority. Sometimes the management team is busy and the waiter simply says no.