You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Christine Lee. Please help me out to change my existing reservation.

ASSISTANT: Sure, I can assist you with changing the existing reservation. Can you please wait a minute?

USER: Sure.

ASSISTANT: Sorry to inform you, I have not found any existing reservation with the name you have provided.

USER: Its ok, no issues. Thank you for helping.

ASSISTANT: You are most welcome. Thank you for reaching us, have a nice day.