You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I want to change my existing reservation, can you please help me in this?

ASSISTANT: Sure. May I know your name?

USER: Sure, my name is Larry Williams.

ASSISTANT: Let me check.

USER: Sure.

ASSISTANT: Sorry Larry, no reservation found by your name.

USER: That's fine.

ASSISTANT: Thank you for contacting us.

USER: My pleasure.