You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Jennifer Johnson.

ASSISTANT: How may I help you?

USER: I want to change my existing reservation.Could you please help me out?

ASSISTANT: Sure, wait a moment.

USER: Ok.

ASSISTANT: Sorry no reservation found for you.

USER: Ok, that's fine. Thank you.

ASSISTANT: You are welcome, have a safe journey.