Some owners of the devices have been known to display the message despite having mobile service available, and now the technology giant has explained that the issue comes a failed component "on the main logic board".
The statement on Apple's official website explained: "Apple has determined that a small percentage of iPhone 7 devices may show 'No Service' in the status bar (even if cellular coverage is available), due to a component that has failed on the main logic board. These affected units were manufactured between September 2016 and February 2018 and sold in China, Hong Kong, Japan, Macao, and the US. See below for iPhone 7 model numbers that are covered in this program. If your device exhibits the symptom described above, Apple will repair your device, free of charge. Your iPhone will be examined prior to any service to verify that it is eligible for this program. This program only applies to iPhone 7."
The company also confirmed it was contacting customers over email if they believed they had paid for a repair related to the glitch to arrange a reimbursement.