You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

USER: I want to attend a marriage in Las Vegas, can you book a ticket?

ASSISTANT: Sure, I can help you with that.

USER: My airport codes are DCA to LAS.

ASSISTANT: Can you please help me with your travelling dates?

USER: My travel dates are 07/27 and 07/29.

ASSISTANT: May I know your name to proceed further?

USER: My name is Michelle Wright.

ASSISTANT: Ok, let me check for the availability of flight. Michelle, I am sorry to inform you that there is no flight available at your request.

USER: No problem.

ASSISTANT: Thank you for contacting us.

USER: Thank you for checking.

ASSISTANT: You are welcome.