Refund of a student promotion

Apple allows returns for 14 days, so you cannot return it in order to buy another with the promotion. So, you are too late. Such promotions have beginning and ending dates as part of the terms and do not include a refund after the fact.

It's probably too late, but that's just an educated guess. This is a user-to-user forum, and most of the people who answer questions here (including me) are not Apple employees.

For a definitive answer, you'd need to contact Apple.