You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Thomas Thomas.

ASSISTANT: How may I assist you today?

USER: I want to book a ticket from SFO to DEN to meet my brother, can you help me in booking?

ASSISTANT: Thomas Thomas, may I know your travelling dates please?

USER: I am departing on 12/27 and return on 12/29.

ASSISTANT: Sorry to inform you, thee is no flight available on your requested dates.

USER: That's ok, thank you for your information.

ASSISTANT: Sorry for the inconvenience, have a great day.