You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am William Clark. I would like to travel from IAD to DFW. Can you please help me to book a ticket?

ASSISTANT: Sure, may I know your trip dates please? Do you have any other requirements?

USER: My travelling dates will be on Feb 12 to Feb 14. I need a connecting flight with economy class.

ASSISTANT: Ok, please wait.

USER: I want to depart in the afternoon. Sure, I will wait.

ASSISTANT: Sorry, there is no flight available as per your request.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: My pleasure.