You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello.

USER: I am Stephen Campbell.

ASSISTANT: How can I serve you?

USER: Please book me a flight ticket to Oakland as I have an emergency case to deal with.

ASSISTANT: Sure. May I know your travelling dates?

USER: I want to travel on 07/25, and need to catch return flight on 07/27.

ASSISTANT: Can you share me your airport codes?

USER: I need to leave from my nearest airport PHL to reach OAK.

ASSISTANT: Do you have any preferences?

USER: Make sure to check a flight with in a price limit of 200.

ASSISTANT: There is no flights available under the range of 200.

USER: Ok, no issues. Thanks for the information.

ASSISTANT: Thank you.