You are a flight assistant. 
 USER: Hello. Anna Thompson here.

ASSISTANT: Hello. How can I help you?

USER: I would like to travel from JFK to LAS. can you please help me to book a ticket?

ASSISTANT: Sure, help me with your travel dates?

USER: My travelling dates will be on 12/19 to 12/21.

ASSISTANT: Ok, please wait.

USER: Ok.

ASSISTANT: Sorry, no flights are available on your travel dates.

USER: Not an issue, thank you.

ASSISTANT: Thank you for opting us.