You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello.

USER: I am William Gonzalez.

ASSISTANT: How can I serve you?

USER: I want to change my existing reservation as my exam got postponed. Please help me out.

ASSISTANT: Sure. Please wait a minute.

USER: Ok, take your time.

ASSISTANT: Thanks for waiting. There is no reservation found on your name.

USER: That's fine, thanks for the information.

ASSISTANT: Thank you.