You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I  help you?

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

ASSISTANT: Sure, may I know your name please?

USER: Myself Jonathan Mitchell.

ASSISTANT: I am sorry no reservation found on your name.

USER: Not an issue. Thank you.

ASSISTANT: You are welcome. Thank you for opting us.