You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you now?

USER: I want to book a ticket from SFO to ATL. Could you book a ticket?

ASSISTANT: Sure, I am happy to help you with that. Can I have your travel dates please?

USER: Departure is Dec, 22 and return date is Dec, 24.

ASSISTANT: Ok, please let me know the timings of your journey.

USER: I would like to depart in the afternoon.

ASSISTANT: Do you have any other specifications?

USER: I would like to prefer economy class.

ASSISTANT: Can I have your good name please?

USER: My name is Michelle Baker.

ASSISTANT: Sorry to inform you that no flight is available to you on your travelling dates.

USER: Thank you.