You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, could you please tell us for what help you approached us?

USER: I would like to attend for a seminar in SFO. Can you please help me to book a flight from ATL?

ASSISTANT:  Sure, may I know your departure and arrival day?

USER: I want to depart on May 19 and need to return on May 21.

ASSISTANT: Ok, could I have your name please?

USER: Elizabeth Davis here.

ASSISTANT: Ok, do you need direct or connecting flight?

USER: I need a direct flight.

ASSISTANT: Ok, do you have any other specifications?

USER: My return time must be in the evening.

ASSISTANT: Sorry, there is no flight on your requested travelling dates.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: You are welcome, have a great day.