On older devices with a worse battery, the phone will show that reduced Maximum Capacity, as well as detail any performance slowdowns due to the decreased battery capacity. On devices that have weaker batteries, the Peak Performance Capability will change to read "This iPhone has experienced an unexpected shutdown because the battery was unable to deliver the necessary peak power. Performance management has been applied to help prevent this from happening again." A small blue hyperlink then says "Disable," which lets you manually turn off your iPhone's performance management.
Apple says that the problematic iPhone 7s were sold in China, Hong Kong, Japan, Macao, and the US between September 2016 and February 2018. The specific model numbers are A1660, A1780 and A1779 and anyone whose phone is displaying a "No Service" message even when signal is available is told to contact their nearest Apple Authorized Service Provider, Apple Retail Store or Apple Technical Support.