If you’re thinking about moving to Sprint’s network to get the iPhone 4S with slow unlimited data, than this may be a good time if you have an iPhone lying around. Beginning on April , customer who trade any iPhone model with Sprint can instantly receive up to $100 credit towards a new iPhone 4S, reports Technobuffalo. This offer however requires an activation of a new line of service with two-year agreement, either on a new account or an existing account. But let’s be honest, you’d be better selling your iPhone somewhere else unless you have an iPhone 3G or older.