You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Robert Turner.

ASSISTANT: How can I aid you Robert?

USER: I january month to attend my friend's birthday I have booked my plane ticket in advance.

ASSISTANT: Ok.

USER: In that existing reservation I want to change my destination code. If it is possible, can you do this for me?

ASSISTANT: Sure. Please wait, let me check.

USER: Ok.

ASSISTANT: Sorry Robert, I do not found any reservation under your name in our database.

USER: I haven't expected this, I will think about that. Thank you for your response.

ASSISTANT: It's my pleasure, have a good day.