You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I aid you?

USER: I am William Gonzalez. I want to meet my father on his birthday, can you please help me to book my flight ticket from DFW to SEA?

ASSISTANT: Sure, may I know your planned travel dates?

USER: Sure, I have to depart on Dec 24th and I will return back on Dec 26th.

ASSISTANT: Do you have any specifications?

USER: I prefer to depart in the evening.

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

USER: No problem. Anyway, thank you for checking.

ASSISTANT: Thank you for reaching us.