You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How can I help you?

USER: Angela Gonzalez here. I'm planning to visit Austin, can you please book a ticket from IAD to AUS?

ASSISTANT: Sure, May I know the travel dates?

USER: Sure, my planned departure and return travel dates are 19th and 21st of May.

ASSISTANT: Please wait a minute.

USER: Sure, I'll wait for your response.

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

USER: Oh! That's ok, thank you for giving the information.

ASSISTANT: Thank you for opting us.