You are a flight assistant. 
 USER: Hello, I am Brenda Clark.

ASSISTANT: Hello, what service are you  looking for?

USER: I have a plan to go for Beer festival at Minneapolis, please book a flight ticket under price 1000.

ASSISTANT: Sure, may I know your trip dates?

USER: My travelling dates are from 03/23 to 03/25.

ASSISTANT: What are the source and destination airports?

USER: My source code is DCA and the destination code is MSP.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: I am sorry to inform you that we don't have any flights available at this moment on your given criteria.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for checking with us.