It would appear that Apple is having a tougher time than expected selling iPhone 7 models. This is in part due to a backlog of iPhone 6s models, which has supposedly led Apple to cut production of its flagship handset. As the story goes, Apple gave its suppliers a heads up that it will be slashing orders of its iPhone handsets by around 10

Source: Hot Hardware – Apple Allegedly Cuts iPhone 7 Production By 10 Percent Due To Sluggish Sales