You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I serve you?

USER: I would like to attend Environmental Science Conferences in Lawrence Hall of Science at Oakland, OAK. Can you book a ticket with a connecting flight?

ASSISTANT: Sure, may I know your name?

USER: My name is Brian Allen.

ASSISTANT: Can I know your travelling dates?

USER: My travelling dates are 04/28 and 04/30.

ASSISTANT: Please provide your source code.

USER: Source is CLT.

ASSISTANT: There is no flight found with your requirements.

USER: Not a problem, thank you for the information.

ASSISTANT: Thank you for contacting us.