You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. In which way I can help you at this moment?

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

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

USER: Andrew Clark.

ASSISTANT: Ok, please hold on 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.