You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: Help me in changing my reservation?

ASSISTANT: Sure, I am here to help you out. May I know your name please?

USER: I am John Clark.

ASSISTANT: Wait a moment please.

USER: Ok.

ASSISTANT: John Clark, we haven't found any reservation under your name in our database.

USER: That's ok, thank you.

ASSISTANT: Thank you for choosing us.