The GSMA Device Registry is a global database that enables users to keep track of any lost or stolen iPhones using the IMEI number. The IMEI number of a device can be found in the Settings app under General > About.
This can be confirmed by an Apple technician who sees a message in their internal MobileGenius or GSX systems notifying them that the device has been marked as missing or lost. Technicians are told in the memo to refuse such repairs.
In an effort to reduce the number of stolen iPhones brought to Apple for repair, the company has instituted a new policy.
Customers who can’t turn off Find My iPhone will be denied service, as the company has previously implemented a policy.