You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: Donald Harris here.

ASSISTANT: Ok.

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

ASSISTANT: Sure, I am here to help you.

USER: Thanks.

ASSISTANT: Could you please help me with your travelling dates?

USER: My travelling dates are from 04/26 to 04/28.

ASSISTANT: May I know your travelling airport codes?

USER: My airport codes are from DCA to BOS.

ASSISTANT: Ok, please wait for a while.

USER: Ok, I will wait.

ASSISTANT: Sorry, no flights found on your requested travelling dates.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you for choosing us, have a nice day.