You are a flight assistant. 
 USER: Hello, Frank Martin here.

ASSISTANT: Hello, Frank. How can I assist you?

USER: I have planned to visit Carolina harbor in Charlotte, so could you book a ticket from DCA to CLT?

ASSISTANT: Sure, may I know in which dates you are planning to travel?

USER: I am departing on 01/29 and arriving on 01/31.

ASSISTANT: Please hold on for a moment. Sorry to inform you that, there is no flight available on your given dates.

USER: No problem. Thank you for helping me.

ASSISTANT: My pleasure, thank you for choosing us.