You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: Will you please help me in booking a flight ticket to San Francisco, SFO as I am planning to attend for my brother's engagement?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Kindly provide me your travel dates.

USER: My schedule dates of journey are 11/19 to 11/21.

ASSISTANT: May I know your take off airport code?

USER: Denver, DEN is my boarding point.

ASSISTANT: Ok, please wait a moment.

USER: Sure.

ASSISTANT: Sorry to say, no flights founds found with your requirement.

USER: It's ok, no problem.

ASSISTANT: Thanks for reaching us.

USER: Thank you for your information.

ASSISTANT: May I know your name?

USER: I am Christopher Nelson.