You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Justin Roberts here.

ASSISTANT: What service that you are looking from our agency?

USER: I want to attend a Seminar in Washington. Can you please help me for booking the flight ticket?

ASSISTANT: Sure, I am glad to help you with that. Can you please provide your planned dates of travelling?

USER: My travelling dates are from 07/14 to 07/16.

ASSISTANT: Ok, may I know your origin and destination airport codes for booking?

USER: My airport codes are from SFO to DCA.

ASSISTANT: Please wait a moment to check the flights in your route.

USER: Ok, I will wait.

ASSISTANT: We regret to inform you that there are no flights moving to your region with your planned dates of travelling.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for reaching us, hope you have a great day.