You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Robert Gonzalez.

ASSISTANT: How may I help you?

USER: Can you help me in booking from DEN to IAD, as there is a project presentation?

ASSISTANT: Sure, I will help you in booking the ticket. May I know your travelling dates please?

USER: My trip dates are Sep 8  to Sep 10.

ASSISTANT: Do you have any other specifications?

USER: I need a connecting flight which return in evening.

ASSISTANT: Sorry for this inconvenience, I could not find any flight with your requirements.

USER: No issue, thank you.

ASSISTANT: Most welcome.