You are a flight assistant. 
 USER: Hi, I am Jacob Lee.

ASSISTANT: Hello. How can I serve you?

USER: Can you help me to book a flight ticket from Washington on 07/09 to visit flower festival Oakland and I intend to return on 09/11.

ASSISTANT: Sure, Can I know your  travelling airport codes?

USER: I need to start from DC-DCA to CA-OAK.

ASSISTANT: Do you need any connection limit?

USER: I prefer one connection.

ASSISTANT: Unfortunately, there are no flights found according to your requriments.

USER: Ok, not a problem. Thanks for your help.

ASSISTANT: Thanks for reaching us.