You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I am Pamela Moore. I am planning to celebrate my birthday in Philadelphia, so please book a economy class flight ticket for me.

ASSISTANT: Sure, may I know your airport codes?

USER: My source and destination airport codes are TX - DFW, PA - PHL.

ASSISTANT: When are you departing and returning back?

USER: My departure day is 09/06, return day is 09/08.

ASSISTANT: Wait a minute.

USER: Sure.

ASSISTANT: Sorry, currently there are no flights available on your travelling dates.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for availing us.