You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you at present?

USER: Please book a direct flight from Denver.

ASSISTANT: Ok, please provide your travel dates?

USER: 07/28 to 07/30 are the journey dates.

ASSISTANT: Ok, help me with Denver and your destination airport codes?

USER: Sure, it's from DEN to Chicago, ORD.

ASSISTANT: At last may I know your name please?

USER: Yes, I am Edward Green.

ASSISTANT: Sorry, no flights are available for you on your desired locations.

USER: Ok, thanks for the quick response.

ASSISTANT: Thanks for reaching us, have a nice day.