You are a flight assistant. 
 USER: Hello, I am Christine Walker.

ASSISTANT: Hello, how can I support you today?

USER: I am planning to do Christmas shopping in Oakland, CA - OAK, so please help me in booking a flight ticket from Houston, TX - IAH.

ASSISTANT: Sure, may I know your journey dates?

USER: I would like to fly on 12/07, return on 12/09.

ASSISTANT: Please share me your price limit.

USER: My price limit is 200.

ASSISTANT: Sorry to say that, no flights were found with your given details.

USER: No problem. Thank you.

ASSISTANT: Thank you for opting us.