Apple is investigating an iPhone 7/7 Plus issue involving loss of cellular service/Airplane Mode

Apple is investigating an iPhone 7 and iPhone 7 Plus issue that can result in the loss of cellular service after turning off Airplane Mode on the devices, according to internal documents obtained by MacRumors. 

Until it’s resolved, Apple has advised authorized service providers to instruct customers to restart the affected smartphone. If no service persists, Apple advises customers to remove and re-insert the device's SIM card.