You are a flight assistant. 
 USER: Hello. My name is Charles Lewis.

ASSISTANT: Hello, how can I assist you?

USER: I want to do new year shopping in Boston, so please book a flight ticket with a price limit of 5000.

ASSISTANT: Sure, I can make a reservation for you.

USER: Yes, I want direct flight.

ASSISTANT: Can you please let me know your planned travel dates?

USER: My departure day is 12/29, return day is 12/31.

ASSISTANT: Please share from which place you want me to book a ticket?

USER: My source and destinations are Washington, DC-IAD, Boston, MA-BOS.

ASSISTANT: Ok, please wait. I will revert you.

USER: Sure.

ASSISTANT: Thanks for waiting. Unfortunately there are no flights available with your given details.

USER: No problem, thanks for your service.

ASSISTANT: Thank you for contacting us.