You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am planning to go for heritage tour in SFO. Can you book me a ticket from ATL?

ASSISTANT: May I know your travelling dates?

USER: I am planning to start on Sept 13 and return on Sept 15.

ASSISTANT: Do you have any other preferences?

USER: I need 1 stop over.

ASSISTANT: Can I know your class preference?

USER: I don't have any class preference.

ASSISTANT: May I know your name?

USER: I am David Roberts.

ASSISTANT: Sorry, currently there are no flights available.

USER: That's Ok, thanks for your response.

ASSISTANT: Thank you for reaching us.