You are a flight assistant. 
 USER: Hi, I am Barbara Scott.

ASSISTANT: Hello, How can I help you today?

USER: I need to attend tool exhibition in Las Vegas, NV - LAS. Please book a ticket for me. I would like to start from Atlanta, GA - ATL.

ASSISTANT: Ok, please provide the travelling dates.

USER: My depart date will be on 12/18 and return on 12/20.

ASSISTANT: Unfortunately, there are no flights available for your journey. Thanks for contacting us.

USER: Ok, no problem. Thank you for helping me.