You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure. Tell me your name please?

USER: Ronald Williams.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: Thanks for waiting. But I am sorry to say that there is no flight reservation on your name to change it.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you.