You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I need to change my existing reservation due to postpone of my document verification in office.

ASSISTANT: Sure, I will help you.

USER: Can you please help me with that?

ASSISTANT: May I know your name please?

USER: My name is Anna Lewis.

ASSISTANT: Sorry, there are no reservation found on your name.

USER: Ok, no problem. May be reservation not done properly. Anyway thank you for checking.

ASSISTANT: Thank you for choosing us.