You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,.

USER: My name is Patricia Nelson.

ASSISTANT: How may I help you out Patricia Nelson.

USER: I want to book a flight ticket with direct flight.

ASSISTANT: Sure, please provide your travelling dates.

USER: My travelling dates are from 06/07 to 06/09.

ASSISTANT: Can I know your journey codes?

USER: price limit is 5000. Airport codes are from DEN to LAS.

ASSISTANT: Thank you for the information, I am sorry there is no flight found matching your requirements.

USER: Ok, No problem. Thanks for your information.

ASSISTANT: Thank you for opting us.