You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Richard Taylor.

ASSISTANT: How can I assist you today?

USER: I planning to meet my friends after a long time, can you book a ticket for me?

ASSISTANT: Sure, I can help you with that. Could you please help me with the airport codes?

USER: I want to travel from PHL and my destination is DFW.

ASSISTANT: May I know your probable travelling dates?

USER: My planning dates are from 09/18 to 09/20.

ASSISTANT: Richard, there is a flight available with price fare 800 and the airline is UA with 1 connection.Can I proceed with booking?

USER: I am planning a flight with low cost, can you help me?

ASSISTANT: I am sorry to inform you that there is no flight available with the lowest price.

USER: It's fine. Anyway, thank you for your help.

ASSISTANT: You are welcome. Thank you for contacting us.