You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: My name is Charles Robinson, I want to book a direct flight to Washington DC to attend a meeting. Can you help me with booking?

ASSISTANT: Sure, please share your journey dates?

USER: I will travel on June 2 and return on June 4.

ASSISTANT: May I know your origin airport code please?

USER: My source airport code is PHL.

ASSISTANT: Do you have any other specifications to be met?

USER: I need my departure and arrival flight in evening. Please book my flight to IAD airport.

ASSISTANT: Sorry, no flights found on your given details.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for choosing us.