You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: I'm Gregory Lee want to attend my sports event in Denver, can you help me to book a ticket from JFK to DEN?

ASSISTANT: Can you please provide your travelling dates?

USER: Sure, my travel dates are 04/29 and 05/01.

ASSISTANT: Please wait for a while.

USER: OK.

ASSISTANT: Thanks for waiting. Unfortunately, there are no flights found.

USER: OK, thank you.

ASSISTANT: Thank you.