You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you?

USER: Can you help me to book a flight ticket from DCA to Austin, AUS?

ASSISTANT: Sure, May I know the travelling dates?

USER: Ok, please a ticket for the dates Aug 19th and Aug 21 respectively.

ASSISTANT: Do you have any connection limit?

USER: Ok, please book a connecting flight if possible.

ASSISTANT: Is there any other requirements?

USER: No.

ASSISTANT: May I know your name?

USER: My name is Patrick Mitchell.

ASSISTANT: Please wait a minute.

USER: Ok, please take your own time.

ASSISTANT: Sorry, No flights found with your chosen dates.

USER: Ok, that is not a problem. Thank you for assisting me.

ASSISTANT: Thank you for opting us.