You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I have planned to participate in Sports festival at Oakland, Can you book a ticket on 07/13?

ASSISTANT: Sure, may I know your return date and Source code?

USER: I intend to return on 07/15. My source is Denver, CO - DEN.

ASSISTANT: please provide your dest code.

USER: My destination code is CA - OAK.

ASSISTANT: May I know your name?

USER: Sure, I am Ronald Rodriguez.

ASSISTANT: Thank you for the information, there is no flight found with your requirements.

USER: Ok, Thank you for your service.

ASSISTANT: Have a good day.