You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I would like to spend some more days with my family, please help me in changing my existing reservation.

ASSISTANT: Please wait a while.

USER: Sure.

ASSISTANT: May I know your name please?

USER: Sure, my name is Jack Williams.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

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

ASSISTANT: Thank you for opting us.