You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, what can I do for you today?

USER: I want to change an existing reservation. Can you please help me out?

ASSISTANT: Sure, it's my pleasure to help you. May I know your good name please?

USER: Sure, my name is Andrew Walker.

ASSISTANT: OK, wait for a moment let me check.

USER: OK.

ASSISTANT: Sorry, no reservation found on your name. Thank you.Have a great day.

USER: OK, thank you for your information.