You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: I want to change an existing reservation, so please help me in changing the reservation.

ASSISTANT: Sure, can I know your good name to proceed further?

USER: Myself Brian Clark.

ASSISTANT: Please wait for some time.

USER: Ok.

ASSISTANT: Sorry, no reservation is found on your given name.

USER: Not an issue. Thank you.

ASSISTANT: Thanks for contacting us.