You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I am Anthony Jackson, I want to book a flight to San Francisco to visit comic-con. Can you book a ticket under fare of 500?

ASSISTANT: Sure, please let me know your travel dates.

USER: I will fly on 03/13 and return on 03/15.

ASSISTANT: May I know your airport codes please?

USER: I will travel from IL-ORD to CA-SFO.

ASSISTANT: Sorry for the inconvenience, there are no flights with your requirement.

USER: Thank you for the information.

ASSISTANT: Thank you.