You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you?

USER: I would like to change an existing reservation, due to some urgent work. Can you please change my reservation?

ASSISTANT: Sure, I am here to help you.

USER: Thank you.

ASSISTANT: Can I know your name please to proceed further?

USER: My name is Stephen Hill.

ASSISTANT: Sorry to inform you that there is no active reservation on your given name.

USER: That's fine, thank you for your service.

ASSISTANT: Thanks for contacting us.