You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: I am Elizabeth Parker want to attend a workshop on 03/25 and intend to return on 03/27. Can you help me to book a flight ticket?

ASSISTANT: Can you help me with your planned airport codes to search a flight?

USER: Sure, my airport codes are PHL and OAK.

ASSISTANT: Do you have any other requirements?

USER: Yes, my flight price should not exceed 200.

ASSISTANT: Sorry, there is no flight is available for you.

USER: Ok fine, thank you.

ASSISTANT: Thank you for choosing us, have a nice day.