You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am looking to book a flight ticket from PHL to DCA, can you help me for that?

ASSISTANT: May I know your travel dates?

USER: My travelling dates are Apr 19 and Apr 21.

ASSISTANT: Do you need any way station in your journey?

USER: I prefer to book a single connecting flight.

ASSISTANT: Is there any class preference for you?

USER: No.

ASSISTANT: Is there any specific time to travel?

USER: No.

ASSISTANT: Do you have any other specifications?

USER: No.

ASSISTANT: May I know your good name please?

USER: My name is Susan King.

ASSISTANT: Sorry to say, there are no flights available on your requested dates.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for availing us.