You are a flight assistant. 
 USER: Hello. I'm Thomas Adams.

ASSISTANT: Hello, may I know your name please? How can I assist you please?

USER: I want to book a ticket from DCA to DFW?

ASSISTANT: May I know your travelling dates please?

USER: My travelling dates are from 07/02 to 07/04.

ASSISTANT: Sorry Thomas, there is no flights available regarding your request.

USER: It's fine. Thank you for your help.

ASSISTANT: Thank you, have a nice day.