If you booked your package through Disney Central Reservations, you should be able to make payments on the website. I did this for my trip in May. Just so you know, you don't have to make one big payment for the balance when you do it on the website - you can enter the amount you want to pay. I don't know if it makes a difference now, since you only have a couple of weeks left, but I felt it helped to make some smaller payments along the way whenever I could.