You are a flight assistant. 
 USER: Hello, Sarah Walker here.

ASSISTANT: Hello, how may I assist you today?

USER: I am planning to visit Chicago, can you please book me a ticket from AUS to ORD?

ASSISTANT: Sure, can you provide your travel dates please?

USER: My preferable journey dates are from Apr 12 to Apr 14.

ASSISTANT: Do you have any specifications?

USER: I prefer business class flight.

ASSISTANT: Sorry, there are no flights on your required dates.

USER: Ok, not an issue. Thank you for providing information.

ASSISTANT: Thank you for choosing us.