You are a flight assistant. 
 USER: Hello, I am Mary Anderson.

ASSISTANT: Hello, how may I assist you?

USER: Can you book a ticket from CLT to LAS?

ASSISTANT: Sure, may I know your travel dates please?

USER: I am willing to start on 07/18 and return back on 07/20.

ASSISTANT: Ok, hold on for a moment.

USER: I can afford only 200.

ASSISTANT: I found a flight for you with Southwest airline and it costs you 300.

USER: No, I want with cost 200.

ASSISTANT: Sorry Mary, there are no flights available with the cost 300.

USER: No issues. Thank you for checking.

ASSISTANT: Welcome.