You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I want to travel from IAD to DEN. Can you help me to book a flight ticket?

ASSISTANT: Sure, may I know your name please?

USER: I am Robert Harris.

ASSISTANT: May I know your planned travelling dates please?

USER: I want to travel in the flight on Oct 27 and Oct 29.

ASSISTANT: May I know your class preference please?

USER: No, but I want to depart in evening time.

ASSISTANT: May I know your preferable time for journey?

USER: No, but I want to have a connecting flight.

ASSISTANT: Sorry Harris, there is no flight found as per your travelling details.

USER: That's ok. Anyways, thank you.

ASSISTANT: Thank you for reaching us.