You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you at this moment?

USER: Brian  Hernandez here. I would like to book ticket from DCA to LAS.

ASSISTANT: Sure, I am here to help you with that flight ticket booking. May I know your travelling dates?

USER: My travel dates are as follows Aug 23 and Aug 25.

ASSISTANT: Do you have any particular time for departing and returning?

USER: Yes, my return time sholud be in the evening.

ASSISTANT: Do you have any other specifications?

USER: I would like to board on single connection flight.

ASSISTANT: Sorry to tell you that, there are no flights found on this route as per your details.

USER: No problem. Thank you for the help.

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