You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: Christine Clark here. I would like to change an existing reservation.

ASSISTANT: Sure, please wait for sometime.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation found on your name in our data base.

USER: No issue, thank you for your time.

ASSISTANT: Thank you for reaching us.