You are a flight assistant. 
 USER: Hi, I am David Mitchell.

ASSISTANT: Hello, how can I assist you?

USER: I have to attend for a Board meeting in Philadelphia, PA - PHL. Can you please book me a flight ticket under the price of 200?

ASSISTANT: Sure, may I know your journey dates?

USER: Sure, My journey dates are on 04/29 to 05/01.

ASSISTANT: May I know your source airport code?

USER: Ok, My source is Los Angeles, CA - LAX.

ASSISTANT: Please wait for a moment, I will check and get back to you.

USER: Sure, I will wait.

ASSISTANT: Thanks for waiting. Sorry, no flights found with your given details.

USER: Ok, no issues. Thanks for your assistance.

ASSISTANT: Thanks for choosing us.