iPhone 6S shutting down unexpectedly? Here's what to do
Apple has admitted that there are a "small number" of iPhone 6S smartphones that have an issue that causes them to unexpectedly shut down. If you have one of these devices Apple says that while this is not a safety issue and only affects a small number of devices, it wants to fix them. Devices affected by the unexpected shutdown issue were made between September and October of 2015 within a limited serial number range.
Apple is pointing out that this isn't a safety issue because it doesn't want people to think that the shutdowns are due to overheating that could possibly lead to similar fire woes as Samsung has suffered with the Galaxy Note 7. Apple says that any user who has a smartphone that shuts down unexpectedly can have the battery replaced if the serial number is confirmed to be in the range of affected devices.
The battery replacement can be done at an Apple Retail Store or an Apple Authorized Service Provider at no cost. Apple notes that the iPhone will be inspected before any service is performed to verify it is in working order and that it is eligible.
The replacement program link at the bottom of the article has links to allow you to find the nearest Apple Authorized Service provider, Apple Retail Store, or to Apple Technical Support.
Wireless carriers aren't participating in this service program says Apple. Before you send your iPhone 6S in for service you need to back your data up to iTunes or iCloud, turn off find my iPhone, and erase data using erase data and settings in Settings > General > Reset > Erase all content and Settings.
Apple notes that if your covered iPhone 6S has any damage like a cracked screen that would impair the battery replacement, the cracked screen or other issue will need to be fixed before the battery can be replaced. Apple will give refunds to owners of iPhone 6s devices who paid to have the battery replaced if it falls in the serial number range.
SOURCE: Apple