I will be trading in/selling my iPhone 5 and using that money towards the purchase of an iPhone 6 Plus with my upgrade through Sprint. I see a lot of places are offering trade-in credit for the old phone. Does anyone know what stores will be able to use the trade-in towards the price of the new phone if I pre-order on the 12th? If not it is not big deal at all as I will sell privately privately on eBay or elsewhere. I just think it would be more convenient to swap out at the time of purchase at a place like Sprint, Best Buy, Apple etc.. Thanks!