You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you now?

USER: I am Eric Walker, I plan to celebrate my birthday with my friend at his place at Oakland.

ASSISTANT: Ok.

USER: Can you help me to book flight on 12/10 and return ticket on 12/12?

ASSISTANT: Sure. Can I have your airport codes?

USER: I will travel from NC-CLT to CA-OAK.

ASSISTANT: Sorry, there are no flights with your requirements.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for picking us.