You are a flight assistant. 
 USER: Hello, Ronald Allen here.

ASSISTANT: Hello Allen, how can I help you today?

USER: I planned to meet my grand parents in CLT, can you please help me to book a flight ticket from DFW?

ASSISTANT: Sure, can I know your trip dates?

USER: I prefer to travel on 12/19 and 12/21.

ASSISTANT: Allen, please be online for a moment.

USER: Sure.

ASSISTANT: There is a flight available in Southwest airlines and the ticket fare is 400 only. Shall I book the ticket for you?

USER: Can you please search for a flight with a fare of 200?

ASSISTANT: Sorry Allen, no flight available with ticket fare 200.

USER: Ok, no problem. Thank you for your time.

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