Mobile operators in a handful of European countries have confirmed they're next to get the two Apple devices.
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Apple has said it will replace devices where the battery is draining too quickly or taking a while to charge up.
Apple is offering iPhone owners up to £175 off a new model if they turn in their unwanted handset.
Phil Schiller, Apple's SVP of global marketing, has told a Chinese newspaper that a cheaper iPhone isn't in the company's product roadmap.