I received this email from Warner Bros re: Superman Returns. I would assume you could email the same person at Warner and they would do what they did for me, which was send me a DHL label which I could mail back with the movie for a return. here is the copy of the email:
Dear Mr. Bunger:
I would be more than happy to help you with this issue. Please respond with an address where I can send you a pre-paid label. Once you receive the label, please return the DVD of Superman Returns in its original case back to me. Once I receive the DVD, I will then order and send you a new one. Please note that this title, for HD, is only available in the combo. I look forward to hearing from you and I apologize for the inconvenience.
Warner Home Video