You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: Can you please help me in changing my reservation?

ASSISTANT: Sure, can I know your name for checking the reservation?

USER: Sure. My name is David Lewis.

ASSISTANT: Sorry Davis, there is no reservation available on your name.

USER: That's ok. Thank you for your valuable time.

ASSISTANT: You are welcome.