The shift is that your phone number no longer has to live on one phone. With iOS 27, which Apple released on September 14, an iPhone feature called Handoff lets one number move between two iPhones. T-Mobile is charging $5 a month for it.
That fee pays for T-Mobile’s carrier-side service, not iOS 27 itself. Apple built the underlying feature into the software, while carrier support, enrollment and pricing sit with the carrier. Apple’s own documentation says only that carrier fees may apply and sends customers to their carrier for the details.
A switch, not a second line
If you are picturing two phones ringing at once on one number, that is not what you are buying. Handoff uses eSIM technology to put the same number on two iPhones, but only one is active on the network at a time. Think of it like a baton pass. Unlock the other iPhone and the number moves to it, with a “Switching to This iPhone” message to confirm. No app, no manual eSIM transfer.
One phone is the main iPhone, which Apple recommends should be the one you use most. The other is secondary. Call Forwarding, Caller ID settings and carrier account management can be handled only from the main one. Apple also says an Apple Watch pairing does not follow the number, so pair the watch with the phone you carry most.
You need to be signed in to the same Apple Account on both phones, with FaceTime and iMessage on the same account, and an eSIM from a carrier that supports the feature. Setup can happen on a new iPhone or afterward in Settings, by choosing Use Number on This iPhone and Another. Nobody has to erase a phone.
Turning it off is the catch
Enabling Handoff is a Settings job. Disabling it is not. Apple says you must contact your carrier to turn it off, and deleting the eSIM from one phone is not enough. Apple warns the carrier may keep charging for Handoff after an eSIM is deleted until you ask it to cancel.
Not everything travels with the number, either. Payment cards added during setup work on both iPhones, and a car key can be shared across the two. Some transit cards, IDs and corporate badges may work on only one at a time.
Carriers and prices
In the US, T-Mobile is the only carrier offering Handoff, so installing iOS 27 on a Verizon or AT&T line does nothing yet. Apple has said Verizon and the UK’s EE will add support by the end of 2026, though neither has announced pricing.
Pricing is anything but standard. Per 9to5Mac, Deutsche Telekom in Germany charges no separate Handoff fee and runs the feature through its existing MultiSIM service, which costs 6.95 euros a month on many plans. Some plans include MultiSIM slots at no extra charge.
Anyone running Dual SIM should note that Handoff works only when both eSIMs come from supporting carriers. Each number is set up separately, but unlocking the other iPhone switches both eSIMs together. The iPhone 18 Pro lineup went on sale September 18, which should give the feature a larger audience.
