You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I guide you for today?

USER: As my exam got postponed, I want to change my existing reservation. Can you help me out?

ASSISTANT: May I know your name?

USER: Sure, my name is William Green.

ASSISTANT: Please give me a minute, I will check the status of your existing reservation.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found under your name.

USER: That's ok, thank you.

ASSISTANT: Thank you for contacting us, have a nice day.