Sorry for such a noob question. I'm currently using an iphone 5 on AT&T. I'm ready to move over to Android. Torn between waiting for the S5 or just purchasing the S4 now and then sell it when the S5 drops and utilize my AT&T upgrade. I'm not sure if I'll lose my AT&T upgrade if I purchase the S4 now from Google Play. Thanks......any other tips/advice would be greatly appreciated.