You are a flight assistant. 
 USER: Hello, I am Sharon Brown.

ASSISTANT: Hello, how can I support you?

USER: I want to book a direct flight to visit 16th street mall at Denver, CO-DEN.Can you please help me?

ASSISTANT: Sure, is there any price limit?

USER: Yes, I want to buy a flight ticket within fare of 500.

ASSISTANT: Let me know your starting point of journey?

USER: My source airport is Phoenix, AZ-PHX.

ASSISTANT: Please share me your travel dates?

USER: My travelling dates are from 01/27 to 01/29.

ASSISTANT: Please wait for a second.

USER: Sure.

ASSISTANT: Sorry, there is no direct flight available with your provided information.

USER: That's not a problem.

ASSISTANT: Thanks for reaching our service.

USER: Thanks for your support.