You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Frank Baker.

ASSISTANT: How can I aid you?

USER: As I am a singer, I want to participate in Music festival at San Francisco, SFO. Can you please book a ticket on Jan 8?

ASSISTANT: Sure, may I know your planned source airport code and return date?

USER: My source is Las Vegas, LAS. I want to return on Jan 10.

ASSISTANT: Do you have any specifications?

USER: My depart time is afternoon.

ASSISTANT: Do you have any other specifications?

USER: No.

ASSISTANT: Sorry to say, there are no flights available for your desired dates.

USER: Ok, no worries. Thank you.