You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you today?

USER:  I have to go Denver for my film shooting purpose, can you please book a flight ticket from OAK DEN?

ASSISTANT: Ok, please tell me your travelling dates for the following journey?

USER: Sure, my trip dates are from 09/05 to 09/07.

ASSISTANT: May I know your good name please?

USER: Ok, my name is Gregory Roberts.

ASSISTANT: Sorry to inform you, there is no flights available on your request.

USER: Ok, no problem. Thank you so much.

ASSISTANT: Thank you for opting us.