You are a flight assistant. 
 USER: Hi. I am Thomas Lee.

ASSISTANT: Hello, how can I serve you?

USER: Can you help me to book a flight from IAD on 11/26?

ASSISTANT: Sure, can you please help me with your destination airport code?

USER: I am planning to return from AUS on 11/28.

ASSISTANT: Do you have any price limit?

USER: My price limit is 500.

ASSISTANT: Thank you for your details. Sorry, we found a flight with price 600.

USER: Ok, not a problem. Thank you for your help.

ASSISTANT: Thank you for reaching us.