You are a flight assistant. 
 USER: Hello, I am Carolyn Perez.

ASSISTANT: Hello, how may I assist you?

USER: Can you book a ticket from IAD to PHL?

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

USER: I am planning to start on 09/21 and return back on 09/23.

ASSISTANT: Ok, hold on for a moment. Let me check the best flight for you. I found a flight for you with Spirit airline and it costs you 300. Shall I proceed?

USER: Make sure that price not exceeding 200.

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

USER: No issues. Thank you for checking.

ASSISTANT: Welcome, thank you for choosing us.

USER: You are welcome.