You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: My name is Dennis Collins.

ASSISTANT: How may I assist you today?

USER: I'm planning a trip to Lake Austin in AUS with my friends, can you book a ticket from IAD?

ASSISTANT: Sure, I will help you Dennis. May I know on which dates you planned to travel?

USER: The travel dates are from 03/31 to 04/02.

ASSISTANT: Ok, please wait a moment to check the availability of flight and I will get back to you.

USER: Ok.

ASSISTANT: Sorry for the inconvenience, no flights available as per your requested dates.

USER: No problem, thank you for your help.

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