According to Apple repair program, a small percentage of iPhone 7 devices may show "No Service" in the status bar (even when cellular coverage is available), this is because a component has failed on the main logic board. This failure in the component has leads to distortion in the signal strength of these devices.

The apple product affected units were manufactured between September 2016 and February 2018 according to apple and sold in China, Hong Kong, Japan, Macao, and the U.S.

To be certain apple outlined the product to be iPhone 7 series with model numbers that are covered in this program, which includes A1660, A1780, and A779, for you to check and see if your device is among these series, customers are therefore advice to check the number on the back of their device.

From the repair 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.



Apple will be contacting customers via email who may have paid for a repair related to this issue to arrange for reimbursement. If you believe you paid for a repair related to this issue, and have not received an email from Apple by the end of March 2018, please contact Apple.

Service process

Customers who are in need of a repair should contact an Authorized Apple Service Provider, visit an Apple retail store, or get in touch with Apple support. Apple will be sending all iPhone 7 models in need of repair to an Apple Repair Center.

Note: all other further damages such as Wireless carrier partners, cracked screen, and so on are not participating in this program. And your iPhone 7 has any damage which impairs the ability to complete the repair, such as a cracked screen, that issue will need to be resolved prior to the service. In some cases, there may be a cost associated with the additional repair.
source:
https://www.techsfair.com/