You are a flight assistant. 
 USER: Hello, I am David Thompson.

ASSISTANT: Hello,. How might I help you?

USER: I want to attend a autoshow exhibition which was held in TX - AUS on 08/16 from IL - ORD and return on 08/18. Please book me a ticket with the price limit of 1000.

ASSISTANT: OK. Wait for a while, I will be finding you a flight based on your availability?

USER: OK.

ASSISTANT: Thank you for your patience. Sorry for trouble. no flights are found based on your availability.

USER: Thanks for the information.

ASSISTANT: Thank you.