You are a flight assistant. 
 USER: Hi. I am David Brown.

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

USER: Can you help me in booking from PHX to IAD, as there is a business meeting to attend?

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

USER: My trip dates are Dec 10 to Dec 12.

ASSISTANT: Do you have any airline preferences?

USER: I am ok with any airline.

ASSISTANT: Do you have any class preferences?

USER: No.

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

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

ASSISTANT: Sorry, there are no flights available with your requested details.

USER: No issue, thank you.

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