You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Margaret Smith here. Can you please help me in booking a flight ticket from SFO to DCA?

ASSISTANT: Sure, can you share your trip dates?

USER: Sure, my travel dates are from Jan 29 to Jan 31.

ASSISTANT: Do you have any preferences?

USER: I need to depart in the morning and return in the evening flight.

ASSISTANT: Give me a minute.

USER: Sure, take your time.

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

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for opting us.