You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Kathleen Allen. Actually, I want to Change my Existing reservation.Can you help me out?

ASSISTANT: Sure, give me a moment.

USER: Sure.

ASSISTANT: Sorry Allen, I didn't find any reservation basing on your details.

USER: That's fine. Thank you for your help.

ASSISTANT: You are welcome.