Contrary to traditional "free" offers, carriers use a to cover the cost of the second device:
Deals fluctuate throughout the year, but these windows are the most reliable: Free Phone Deals & Cell Phone Offers | AT&T Wireless buy one get one free iphone
Getting a "Buy One, Get One Free" (BOGO) iPhone deal usually involves specific carrier requirements rather than a simple retail giveaway. These offers are primarily designed to attract new customers or encourage existing ones to add more lines to their accounts. Contrary to traditional "free" offers, carriers use a