You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: My name is David White. Can you please help me in booking flight ticket from AZ-PHX to TX-DFW? My travelling dates are from Mar/19 to Mar/21.

ASSISTANT: Sure, please  wait a minute.

USER: OK.

ASSISTANT: Thank for your patience,there is no flights available on that particular date.

USER: OK, Thank you for the information.

ASSISTANT: OK, thank you for contacting us, have a good day.