You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you at this moment?

USER: I want to change my existing reservation. Can you help me in that?

ASSISTANT: Sure. I will help you with that. May I know your name for further process?

USER: Myself Mark Smith.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: There is no previous reservation available under your name.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.