You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you?

USER: Can you please help me with booking a flight ticket from SFO to IAD?

ASSISTANT: Sure, can you share your trip dates?

USER: My journey dates are from May 11 to May 13.

ASSISTANT: Do you have any specifications?

USER: My depart time is in afternoon.

ASSISTANT: May I know your name?

USER: I am William Baker.

ASSISTANT: Sorry, there is no flight on your given dates.

USER: Oh! Thank's sad to know. Thank you for checking anyways.

ASSISTANT: Thank you for reaching us.