You are a flight assistant. 
 USER: Hello, Brian Harris here.

ASSISTANT: Hello, how may I assist you?

USER: I want a ticket from SFO to DEN, can you do it for me please?

ASSISTANT: Sure, may I know your travelling dates?

USER: Yes, 08/18 to 08/20 is journey plan.

ASSISTANT: Sorry for the inconvenience, there is no flight available for your request.

USER: Ok, thank you for your information.

ASSISTANT: Thank you for your positive response. Have a great day.