These discounts are almost always issued as monthly bill credits. If you leave the carrier before the 24- or 36-month term ends, you lose the remaining credits and must pay the full device balance.
Buying from an Apple Store or Apple.com is the best option for users who want maximum flexibility and a streamlined experience. where do i buy an iphone
Apple often provides an immediate discount on your new phone when trading in an old device, whereas carriers may spread that credit over 24 or 36 months. These discounts are almost always issued as monthly