You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: I am Margaret Lopez. I want to book a flight ticket from Denver to Chicago.

ASSISTANT: Ok, may I know your price limit?

USER: Sure, my price limit is 200.

ASSISTANT: Can you please provide me your planned journey dates?

USER: My departure is 08/18 and return date on 08/20.

ASSISTANT: May I know your source and destination airport codes?

USER: I am planning to visit Navy Pier in IL - ORD and source from CO - DEN.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, no flights found with your given dates.

USER: Not an issue. Thanks for your service.

ASSISTANT: Thank you for choosing us.