You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I serve you?

USER: Please change my existing reservation, owing to an emergency.

ASSISTANT: Sure, may I know your name to check your details?

USER: I am Mark Smith.

ASSISTANT: Please wait a moment.

USER: Ok.

ASSISTANT: I regret, there is no reservation found on your name.

USER: Thanks.

ASSISTANT: Thank you for reaching us.