You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: William Wright here.

ASSISTANT: How may I guide you today?

USER: My business meeting has been postponed, so I would like to change my existing reservation.

ASSISTANT: Sure, I will help you with that.

USER: Thanks.

ASSISTANT: Please wait for a minute.

USER: Ok, take your time.

ASSISTANT: I am sorry to say that there is no reservation found under your details.

USER: It's ok, not an issue.

ASSISTANT: Thank you for contacting us.

USER: Thank you so much for your help.