I used to work in a registrar's office. Don't call and threaten. Just check and see if hand delivery will work. If it will, go to the school with a box of Trader Joe's chocolates and some snacks and politely tell them your situation, and ask that they please do you the favor of processing them then.... Being nasty will not help them want to help you out. But I always went out of my way to help out the nice students.