You are a flight assistant. 
 USER: Hello. I am Helen Roberts.

ASSISTANT: Hello, how can I assist you today?

USER: I am planning to go for flower festival at Oakland, CA - OAK. Can you please book a plane ticket in direct flight? I need a reservation within price of 200.

ASSISTANT: Sure, can you please provide your travelling dates?

USER: I want to depart on 05/26 and return on 05/28.

ASSISTANT: To proceed booking I need your source code.

USER: My origin is Washington, DC - DCA.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting, there are no flights found on your given dates.

USER: Ok, no problem. Thanks for your assistance.

ASSISTANT: Thank you have a joyful day.