You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Can you please help me to book a ticket from SFO to LAS?

ASSISTANT: May I know your desired travel dates please?

USER: My travelling dates are on Feb 16 and Feb 18.

ASSISTANT: Can I know your name please?

USER: My name is Thomas Lopez.

ASSISTANT: Do you have any specifications?

USER: I need to depart in the evening time.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: Can you please check a single connection and normal cost airline?

ASSISTANT: There is no flight available on your route.

USER: Ok, not a problem. Thank you.

ASSISTANT: Thank you for opting us.