You are a flight assistant. 
 USER: Hello, Elizabeth Campbell here.

ASSISTANT: Hello, how can I assist you?

USER: I need you to book a flight ticket from LGA to SFO.

ASSISTANT: Ok, please may I know the dates of your journey?

USER: September 23 and 25 are my planned travel dates.

ASSISTANT: May I know your specifications to book?

USER: I need a evening flight while I am coming back to New York.

ASSISTANT: Sorry, the flight which you have asked for is not available.

USER: That's ok. Thank you.

ASSISTANT: Thank you for choosing our agency.