You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: Jerry Brown here. I want to change my existing reservation, due to some health problems. Can you help with it?

ASSISTANT: Sure, I am mirthful to help you with that reservation change.

USER: Thank you.

ASSISTANT: Please hold for a moment, let me check your previous reservation status.

USER: Ok, sure.

ASSISTANT: I have found your previous reservation with your name. Can you please provide your new preferable airport codes?

USER: My airport codes are AUS and EWR.

ASSISTANT: May I know your new travelling dates, please?

USER: My travel dates are Dec 2nd and 4th.

ASSISTANT: Do you have any other specifications?

USER: My depart time must be in the evening.

ASSISTANT: There is no flight found on this route as per your travel dates.

USER: Ok, no problem. Anyways, thank you.

ASSISTANT: Thank you for reaching us, have a great day.