You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: Thomas Hill here.

ASSISTANT: Yes, tell me.

USER: I would like to change my existing reservation, because on that day I have to attend function.

ASSISTANT: There is no reservation with your name.

USER: Ok, that's fine.

ASSISTANT: Please visit us next time. Have a nice day.

USER: Thank you for your services.