You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: I am Thomas Perez. I am planning to book a ticket to attend a meeting at IAD. Can you please help me out to book a ticket from OAK?

ASSISTANT: Sure, please provide me your travelling dates.

USER: I would like to travel on Sept 18 and return back on Sept 20.

ASSISTANT: Sorry, I could not find any flight with your travelling dates.

USER: That's fine, thank you for your service.

ASSISTANT: My pleasure.