You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I best serve you today?

USER: I am Scott Hall. Can you book a flight ticket from DCA to PHL?

ASSISTANT: Sure, when are you planning to travel?

USER: Apr, 2 and Apr, 4 are my travelling dates.

ASSISTANT: Do you need a connecting flight?

USER: Yes, I need a connecting flight.

ASSISTANT: Which class do you want to fly?

USER: I want to travel in business class only.

ASSISTANT: May I know your depart and return time?

USER: My depart time should be at evening.

ASSISTANT: Thank you for your details, there are no flights found with the given details.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you.