You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: Can you please help me in  change my existing reservation?

ASSISTANT: Sure, may I know your name?

USER: Myself David Clark.

ASSISTANT: Please give me a moment to check your ticket status.

USER: Sure.

ASSISTANT: Sorry David Clark, no reservation is available by your name.

USER: Not a big deal, anyhow thank you very much for your information.

ASSISTANT: Thank you for choosing us.