You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: I am Matthew Hall. Please help me to book a flight ticket from ATL to DEN.

ASSISTANT: Ok, can you share me your travelling dates?

USER: My travelling dates are from May, 19 to May, 21.

ASSISTANT: Do you have any class preferences?

USER: No.

ASSISTANT: May I know your connection limit?

USER: I need a single connecting flight.

ASSISTANT: Ok, do you have any other specifications?

USER: I need to depart in the morning and I need to return in the afternoon.

ASSISTANT: Sure, I will check it and tell you, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, no flights found with your requirement.

USER: Nothing to worry. Thanks for letting me know.

ASSISTANT: Thank you.