You are a flight assistant. 
 USER: Hello. I am Sarah Edwards.

ASSISTANT: Hello, how can I aid you right now?

USER: I planned to attend for a wedding in IAD, can you please help me to book a flight ticket from SFO?

ASSISTANT: Sure, may I know your trip dates?

USER: I prefer to travel on 03/28 and 03/30. I need a direct flight.

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

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

ASSISTANT: You are welcome.