You are a flight assistant. 
 USER: Hello, David Baker this side.

ASSISTANT: Hello, how may I assist you?

USER: I am having an audition at Denver. Can you book a ticket for me?

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

USER: I am planning to start on 01/21 and return back on 01/23.

ASSISTANT: Ok, may I know your airport codes please?

USER: Search for the flights flying from PHL to DEN.

ASSISTANT: Ok, hold on for a moment. Let me check the best flight for you.

USER: Taker your time.

ASSISTANT: Sorry David, there are no flights available on your requested dates.

USER: No issues. Thank you for checking.

ASSISTANT: Welcome, thank you for choosing us.

USER: You are welcome.