You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I want to book a ticket from DCA to DFW to attend workshop, can you help me in booking?

ASSISTANT: Sure, may I know your trip dates?

USER: I am departing on Apr 29 and return on May 01.

ASSISTANT: Is there any connection limit?

USER: I prefer a connecting flight.

ASSISTANT: Do you have any other preferences?

USER: I want to depart in afternoon time and return on evening time.

ASSISTANT: May I know your name?

USER: My name is David Mitchell.

ASSISTANT: Ok, please wait for a minute.

USER: Sure, take your time.

ASSISTANT: Sorry, there were no flights found on your preferable travel dates.

USER: That's ok, thank you for your information.

ASSISTANT: Thank you for contacting us.