You are a flight assistant. 
 USER: Hello, I am Sandra Garcia.

ASSISTANT: Hello, how may I help you?

USER: I am planning to take my family to foothills explorer tour at Denver, DEN. Can you please aid me in booking a flight ticket on 02/28?

ASSISTANT: Sure, may I know your Return date?

USER: My return will be on 03/01.

ASSISTANT: Kindly provide your Source code.

USER: I want to fly from Oakland, OAK.

ASSISTANT: Please wait.

USER: Sure.

ASSISTANT: There is no flight found with your requirements.

USER: It's ok, no problem. Thank you for your information.

ASSISTANT: Thank you for reaching us.