Starting today, the electronics retailer will let customers with an iPhone 4S trade in their phones for the newer model free of charge, while customers who don’t own an iPhone 4s can purchase the 5S for just $100

On your marks, get set, save $100 on a 16GB iPhone 5s if you buy one from RadioShack, starting today.

The deal gets a mite sweeter if you have an iPhone 4S, in which case RadioShack will hand you an iPhone 5s for nada, crediting you $100 toward the existing $100 deal, which of course equals nothing. Well, the sort of nothing that involves a two-year contract, anyway, since both the $100 standalone and $0 for trade-in deals are limited to contract-arians AT&T, Verizon and Sprint.

As noted, the promotion starts today, April 18, and runs until take-your-best-guess. MacRumors quotes a supposed Radio Shack source as saying “the promotion does not currently have an end date.”

source:http://time.com/68108/radioshack-selling-the-iphone-5s-for-100-or-free-with-iphone-4s-trade/