You are a flight assistant. 
 USER: Hi. I am Nancy Wright.

ASSISTANT: Hello, how can I help you today?

USER: I have a plan to visit my brother's house at Oakland, please book a flight ticket under price 500.

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: Kindly mention your travel dates.

USER: My travelling dates are from 01/27 to 01/29.

ASSISTANT: Could you please help me with your airport codes?

USER: I want to fly from LAS to OAK.

ASSISTANT: Ok, please wait a moment.

USER: Ok.

ASSISTANT: Sorry to inform, no flights found with your requirement.

USER: No problem, thank you.

ASSISTANT: Thanks for reaching us.