A "carrier-locked" phone (also called SIM-locked or network-locked) is a device configured via software to work exclusively with SIMs from the carrier that sold or financed it. This restriction is almost always applied when the phone is bought on an installment plan or bundled with a discounted rate plan.

From the carrier's point of view, the goal is to make sure the customer stays on their network until the contractual obligations or payment plan are complete. For the traveler, though, this has one very concrete consequence: as long as the lock is active, the phone will reject any SIM or eSIM profile that doesn't belong to that specific carrier.

It affects both, and this is exactly where most of the confusion comes from. The lock isn't a limitation of the physical SIM slot — it's a restriction applied at the device's firmware level: the phone checks the identity of the network it's connecting to, regardless of whether that connection comes through a plastic card or an eSIM profile downloaded via QR code.

The practical result is identical in both cases: if you try to install an eSIM from a carrier different from the one your phone is tied to, the device will reject it with a message like "Invalid SIM" or "SIM not supported", exactly as it would with a physical card.

Almost all eSIM guides focus on the compatibility of the phone model, listing which iPhones or Samsungs technically support eSIM. That matters, but it only covers half the problem: a model can be perfectly compatible with eSIM technology and, at the same time, be locked to a single carrier.

People who bought their phone on an installment plan often never find this out, simply because they never had a reason to insert a SIM other than the original one. The problem then surfaces at the worst possible moment: right after landing, with the eSIM QR code ready and no alternative data connection available.

Apple provides a simple, free built-in check. Go to Settings > General > About and scroll to "Carrier Lock". If it says "No SIM restrictions", your iPhone is unlocked and can accept an eSIM from any compatible carrier.

If instead it shows the name of a specific carrier, or a message like "SIM Locked", the device is tied to that network. For extra confirmation, the definitive test is to insert a physical SIM from a different carrier than the original one and see if the phone recognizes it.

Unlike iOS, Android doesn't have a single universal screen showing lock status: the procedure varies from manufacturer to manufacturer. The single most reliable method remains the practical test: insert a physical SIM from a different carrier and check whether the phone connects normally to the network.

Alternatively, many manufacturers offer dedicated service codes: on Samsung, for example, dialing *#7465625# shows the network lock status; on many other Android phones, dialing *#*#2846579#*#* opens a service menu with a SIM status check. If the message shows something like "NW_LOCKED", the phone is locked; if it shows "SIMLOCK_DEACTIVE", it's free.

The IMEI (International Mobile Equipment Identity) is the unique identifying number of every mobile device. You can find it by dialing the free code *#06# on the phone's keypad, or in the device settings (on iPhone: Settings > General > About).

Once you have the IMEI, you can give it to your carrier's customer service for an official lock-status check, or use one of the IMEI-checking services available online: this is especially useful if you're considering buying a used phone, wherever you are, and want to check the lock status before even seeing it in person.

It means the phone is fully unlocked: it accepts SIMs and eSIMs from any compatible carrier, in any country. This is the ideal state for travelers, because it eliminates any risk tied to carrier lock from the start.

If instead the screen shows the name of a specific carrier, or wording other than "No SIM restrictions", the device remains tied to that network until an unlock is requested and completed, as we'll cover later in this guide.

It's not an exclusively American phenomenon at all, even though how common it is varies a lot by region. In the United Kingdom, since December 2021 the regulator Ofcom has banned carriers from selling locked phones: most devices bought there in recent years are therefore already factory-unlocked, regardless of whether they were bought on an installment plan.

In Italy, SIM lock has long been regulated (AGCOM decision 9/06/CIR) and was historically used by only a handful of carriers; today, most phones sold on installment plans by major Italian and European carriers are already unlocked, because the financing plan ties you to the installment payments but doesn't necessarily lock the SIM. The picture changes, however, outside the US, EU and UK: in many countries across Latin America, Asia and the Middle East, branded phones sold on installment plans by local carriers often remain locked, following logic very similar to the US model. The practical rule stays the same wherever you bought your phone: check it before you travel, and don't assume anything based purely on the country of purchase.

The US market works very differently from the European or British one: most phones aren't bought at full price, but through installment financing plans offered directly by carriers like AT&T, Verizon and T-Mobile, often bundled with significant discounts on the device price, and there's no blanket ban on locking in the US like the one Ofcom introduced in the UK.

To protect against fraud and to make sure the customer completes payment, carriers lock the phone to their network for the entire duration of the financing (or for a minimum period of line activity). Anyone who instead buys a device at full price from Apple, Samsung, Google, or a retailer like Best Buy without a carrier financing plan, almost always receives an already factory-unlocked phone, even in the US.

AT&T requires the device to have been purchased or activated at least 60 days earlier, to be paid off in full (or with the installment plan balance at zero), and the account to be in good standing: once these conditions are met, the unlock usually happens automatically within 24-48 hours.

T-Mobile instead requires the line to have been active for at least 40 days and, if the phone is financed or leased, to be paid off in full: the request is made through the T-Mobile app and is generally processed within a couple of business days.

Verizon, historically the most flexible, changed its policy during 2026: automatic unlocking is no longer guaranteed within the short timeframes its customers were used to, as we explain in the next question.

On January 12, 2026, the FCC (the US telecommunications regulator) granted Verizon a waiver from the rule that, since 2007, had required automatic unlocking of phones within 60 days of activation, regardless of payment status. It was the only rule of its kind still binding for a major US carrier.

From that point on, for devices purchased on or after January 27, 2026, Verizon keeps the lock in place until the phone is paid off in full, with an additional 35-day delay for certain online payment methods. Devices purchased before that date remain subject to the old 60-day rule. For anyone traveling with a recently purchased Verizon iPhone, this means it's no longer enough to "just wait two months": you need to actively check the terms of your plan before assuming the phone is unlocked.

If your phone is locked to a carrier different from the one the eSIM profile you want to install belongs to, the device will reject it: it's not a matter of plan compatibility, but of a restriction set directly in the phone's firmware, regardless of which country you bought it in.

The most solid solution, before going ahead with a travel eSIM purchase, is to request an unlock from your carrier well in advance. There are no reliable shortcuts to bypass the lock without going through this official request, and unofficial methods can compromise the device's warranty or security.

• Get your IMEI by dialing *#06# or checking the phone's settings.

• Check your carrier's requirements: device paid off in full, minimum number of days of line activity, account in good payment standing.

• Submit the unlock request through your carrier's app or customer service, providing the device's IMEI.

• Confirm the unlock went through by re-checking the status in settings (or testing with a different carrier's SIM) before considering the process complete.

The ideal time is when you book the trip, not when you pack your bags. Unlock requests can take anywhere from 24 hours to several business days depending on the carrier and country, and if the phone was bought recently or the financing hasn't been paid off yet, you might have to wait until you meet the minimum requirements (days of line activity, financing balance) before you can even submit the request.

Checking weeks in advance gives you time to handle any unexpected issue, without having to worry about connectivity in the hours before departure.