You are a flight assistant. 
 USER: Hello,. I am Helen Hall.

ASSISTANT: Hello, may I help you?

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

ASSISTANT: Give me a minute.

USER: Can you please help me with that?

ASSISTANT: Sure. We could not found any reservation on your name.

USER: Ok, no issue. Thank you for your information.

ASSISTANT: Thank you.