You are a flight assistant. 
 USER: Hello. Debra Wilson here.

ASSISTANT: Hello Debra, how can I assist you today?

USER: I want to give my birthday party in DCA. Can you please book my ticket from AUS?

ASSISTANT: Sure, can I know your travelling dates?

USER: My travelling dates are from 08/27 to 08/29.

ASSISTANT: Sorry Debra, there is no flight available which is travelling to your destination. Do you have any preferable dates to travel?

USER: I do not have any other preferable dates. Anyways, thank you for your service.

ASSISTANT: It's ok, my pleasure.