A recent demo suggests iOS 27's iPhone Relay would let one phone number move between two iPhones, with one set as the main device and the other as a companion.
The number would reportedly switch to whichever iPhone is unlocked, sparing users from manually transferring an eSIM while keeping cellular settings tied to the primary phone.
Two separate eSIM profiles appear to stay linked through the same carrier account, indicating the feature depends on carrier support and could vary by region.
Apple briefly acknowledged the capability at WWDC 2026 and confirmed number switching between two iPhones, but it has not yet provided a full official explanation.