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

ASSISTANT: Hello, how may I support you?

USER: I want to go to Philadelphia for attending a family function, can you please assist me in booking a ticket for direct flight?

ASSISTANT: Sure, may I know when do you want to make your journey?

USER: I want to start my journey on 09/10 and intend to return on 09/12.

ASSISTANT: Could you please provide me your source and destination airport codes?

USER: My source and destination airport codes are WA-SEA and PA-PHL.

ASSISTANT: How much can you spend to buy your ticket?

USER: I can spend upto 5000 on my ticket.

ASSISTANT: Thanks for providing your essentials. There are no flights available at this moment.

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for choosing us.