You are a flight assistant. 
 USER: hi.

ASSISTANT: Hello, how can I help you the best?

USER: I am Samantha Nelson. I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Ok sure, I can help you with that.

USER: Thank you.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: Sorry, no reservation has been found with your name in our records.

USER: Ok, no problem.

ASSISTANT: Thanks for consulting us, have a nice day. Visit Again!.

USER: Thanks for your information.