You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

USER: I am James Anderson. Can you help me to book a connecting flight from DEN to DFW?

ASSISTANT: Can you please share on what dates you are willing to travel?

USER: I want to fly on 27 Dec and return on 29 Dec.

ASSISTANT: Do you have any class preferences?

USER: No.

ASSISTANT: Do you have any airline preferences?

USER:  No, I would like to return in the evening.

ASSISTANT: Do you have any other requirements that you are looking for?

USER: No.

ASSISTANT: Sorry, there are no flights available at your request.

USER: It's ok, not a problem, thank you.

ASSISTANT: Thank you for contacting us, have a nice day.