You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: Can you please book a flight from JFK to IAD?

ASSISTANT: Sure, may I know your planned trip dates?

USER: I want to depart on July 21 and need to return on July 23.

ASSISTANT: Do you have any connection limit?

USER: Yes, I need a connecting flight.

ASSISTANT: Is there any class preference?

USER: No.

ASSISTANT: Do you have any other specifications?

USER: I prefer an normal-cost airline to travel.

ASSISTANT: Please forward your name.

USER: David King.

ASSISTANT: There are no flights found on your specified trip dates.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for availing us.