Found this discount via a private channel. It works for new activations or existing users adding a new line of service - All information at
T-Mobile Offers - STUDENTRATE MEMBERS
You should place your order over the phone @ 1 866 464 8662 and use the promo code 13997 TMOFAV , you get 10% discount on your monthly bill + waived activation fees + free 2 day shipping . The customer service rep will apply the discount for you. Say that you are a student, and member of Student rate. They may ask you for your student ID number so have it ready.
Flyer is attached