You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Benjamin Lopez here.

ASSISTANT: How may I help you?

USER: Reserve a flight ticket that is from ATL to DEN.

ASSISTANT: Sure, could you please share your planned dates?

USER: My travel dates are 12/25 to 12/27.

ASSISTANT: Please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, there is no flight is available for you.

USER: Ok, not a problem.

ASSISTANT: Thank you for choosing us, have a nice day.

USER: Thank you.