I'm an emailer... I don't like to call if I can avoid it. I emailed them with the specifications they asked for (listed below from their website). I emailed them on the 18th, they sent me a confirmation email on the 22nd. Not the best response time, but they do reply... if you're going too soon for that, try calling between 9am and noon - you might have better success getting a live person.
For reservations, call (407) 224-4012 or email
diningreservations@universalorlando.com For email reservations, make sure to include your name, contact telephone number, and party size along with the date you'd like to attend.