You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I would like to change my existing reservation, please help me out.

ASSISTANT: Sure, I will help you with the change of flight reservation. May I know your name please?

USER: Sure, my name is Samantha Davis.

ASSISTANT: Thanks for waiting patiently. But I regret to inform you that that there is no flight reservation on your name to change it.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you.