You are a flight assistant. 
 USER: Hello, Jennifer Baker here.

ASSISTANT: Hello, how may I aid you today?

USER: I want to spend my vacation at Philadelphia. Please book a flight ticket.

ASSISTANT: Sure, may I know your source airport code?

USER: My journey starts from IAD.

ASSISTANT: Can I know your planned travel dates?

USER: I start on September 18 and return back on 20th of the same month.

ASSISTANT: Do you have any other preferences?

USER: I need to take rest in my journey.

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: Sorry, there were no flights found on your preferable travel dates.

USER: Ok, thanks for your time.

ASSISTANT: Thank you for choosing us.