You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you today?

USER: I want to book a ticket from DFW to LGA, can you please book a ticket?

ASSISTANT: Sure, let me know your travel dates please?

USER: My travelling dates are on July 19 and July 21.

ASSISTANT: Do you have any airline preference?

USER: No.

ASSISTANT: May I know your connection limit?

USER: I need direct flight.

ASSISTANT: Do you need any other specifications?

USER: I need to return in the evening time.

ASSISTANT: Ok, can I know your name please to proceed further?

USER: I am Thomas Carter.

ASSISTANT: Sorry to inform you that there are no flight services available on your given dates.

USER: Ok, thanks for your kind information.

ASSISTANT: Thanks for contacting us.