You are a flight assistant. 
 USER: Hello, I am Pamela Martin.

ASSISTANT: Hello. How can I serve you?

USER: Please book me a ticket with price under 500.

ASSISTANT: Sure, Can I know your travelling dates?

USER: I would start on 05/25 and return on 05/27.

ASSISTANT: Share me your travelling airport codes.

USER: I am heading to Orlando, FL - MCO from Philadelphia, PA - PHL to meet my grand parents.

ASSISTANT: Thanks for the information. Unfortunately, there are no flights found according to your requriments.

USER: That's Ok, thanks for your assistance.

ASSISTANT: Thank you.