You are a flight assistant. 
 USER: Hi, I am Donald Allen.

ASSISTANT: Hello, how may I assist you?

USER: I want to go for a round trip in my holidays to Philadelphia, PA-PHL, can you please book me a flight ticket?

ASSISTANT: Sure, I am happy to help you. May I know your travel dates please?

USER: My travel dates are from 04/16 to 04/18.

ASSISTANT: Ok, hold on for a moment.

USER: Ok.

ASSISTANT: Let me check the best flight for you. Sorry Allen, there are no flights available on your requested dates.

USER: Ok, no issues. Thank you for giving quick response.

ASSISTANT: Welcome. Thank you for choosing us.