You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

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

ASSISTANT: Sure, may I know your name?

USER: Betty Johnson here.

ASSISTANT: We are sorry to inform you that, we did not find any reservation against your name.

USER: Ok, no problem.

ASSISTANT: Thank you.

USER: Thank you for checking.