You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you out?

USER: I would like to change my existing reservation, can you please help me out?

ASSISTANT: Sure, I will help you in changing the reservation. May I know your name please?

USER: Sure, my name is David Smith.

ASSISTANT: Sorry, there are no reservations found.

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

ASSISTANT: Thank you.