I just bought it and I decided that I don’t need it after all.
I’m afraid unless items included in the order are backordered, what you ask isn’t generally possible. Once orders move to the fulfillment queue (almost instant), Republic’s ordering system doesn’t allow for cancellation. You may return the unwanted items as outlined here: Money Back Guarantee. If the order can be cancelled, you’ll see the option here: Orders & Payments | Republic Wireless.