You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: I am Andrew Lee. I need to book a flight ticket from DCA to LAS. Please help me in booking a flight ticket.

ASSISTANT: Sure, let me know your travelling dates.

USER: My travelling dates are from Feb, 08 to Feb, 10.

ASSISTANT: Can you please share your connection limit.

USER: Yes, I need a single connecting flight.

ASSISTANT: Is there any specifications?

USER: My depart and return time should be in evening.

ASSISTANT: Sorry, there are no flights found based on your details.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us.