You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello,.

USER: I am Kevin Lee.

ASSISTANT: On what way, can I help you today?

USER: I want to book a flight ticket from Austin AUS  to attend a robotic workshop at Washington, PA-PHL., can you help me to book a flight ticket? My landing point is DCA.

ASSISTANT: Please be patient, while giving your journey details. Ok, On what dates you have preferred to travel?

USER: I would like to travel on 05/15 to 05/17.

ASSISTANT: Ok, please be wait.

USER: Sure.

ASSISTANT: Thanks for waiting. Sorry Kevin Lee, no flights found on your journey dates for your journey.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: Thanks for opting us.