There's no way to call a Disney resort directly; all calls to the published resort numbers go to a call center. Which in your case is OK, because they can add your request to your reservation.
Well, let me amend that. If you booked through Disney - a "cash reservation" as opposed to DVC points, you can call and get transferred to the call center, or just call the main reservation line.
If you're a DVC member and you booked with your own points, you would call DVC Member Services with your requests. If you rented points for your stay, the member who made your reservation will have to call Member Services for you. They will only speak with the owner of the points.