You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I serve you?

USER: I would like to change my existing reservation due to postpone of my documents verification at Denver. Could you please help me?

ASSISTANT: Sure, Please wait a second.

USER: Sure.

ASSISTANT: May I know your name?

USER: I am Larry Walker.

ASSISTANT: Sorry, No reservation found on your name.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for choosing us.