At its core, an unlocked GSM phone is simply that: a phone not “locked” into a single carrier’s network. Since an unlocked GSM phone is not tied to any carrier, you are free to insert your active GSM SIM card into any unlocked phone and start making calls.
https://www.amazon.com/gp/feature.html?ie=UTF8&docId=566955
Unlock device. 1  Learn how to request an unlock code to allow your AT&T phone, tablet, mobile hotspot, or other device to operate on another compatible wireless network. 2  Learn how to get the PIN Unlock Key (PUK) code to unlock your SIM card. Devices display Enter PUK after more than three wrong PIN entries.
https://att.com/esupport/article.html#!/wireless/KM1008728
Cell Phone Unlocking FAQs. When cell phone users change between compatible wireless service providers, they have the option of “unlocking” their phones to use on their new service provider’s network.
https://www.fcc.gov/consumers/guides/cell-phone-unlocking-faqs
To unlock your AT&T phone or tablet to work on another wireless carrierâs network: 1  Go to att.com/deviceunlock (page best viewed from a desktop or tablet). 2  Read and agree to the eligibility requirements to unlock your device. 3  Complete and submit the form.  You'll receive a confirmation email with your unlock request number.
https://att.com/esupport/article.html#!/wireless/KM1008728
An unlocked cell phone is a device that can be used on any carrier that supports that phone. A locked cell phone, in contrast, is fixed to a single carrier. The lock is simply software on the cell phone that prevents the device from recognizing a SIM (Subscriber Identity Module) card from a new carrier.
https://wm15.walmart.com/electronics-resource-center/smartphones/wireless-101/what-is-an-unlocked-cell-phone/
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It's important to understand that only some kinds of phones can be unlocked, namely phones that are compatible with the GSM (Global System for Mobile Communications) network. GSM phones contain a small, removable card, known as a SIM (Subscriber Identity Module), that is programmed with your subscription information and phonebook. A SIM card can be removed and placed in other GSM phones, allowing you to quickly and easily change handsets while retaining your contacts and carrier service.
https://www.amazon.com/gp/feature.html?ie=UTF8&docId=566955
Unlock device. Learn how to request an unlock code to allow your AT&T phone, tablet, mobile hotspot, or other device to operate on another compatible wireless network. STEP-BY-STEP. If you have a myAT&T account, you can verify your device is eligible before you submit a request to unlock your device.
https://att.com/esupport/article.html#!/wireless/KM1008728
Unless you purchased a phone or device specifically sold as “unlocked” at the point of purchase, you should assume that it is locked to a specific service provider’s network. This is true whether you purchase the device from a service provider, a retail outlet or through a third-party.
https://www.fcc.gov/consumers/guides/cell-phone-unlocking-faqs
Benefits of an unlocked cell phone. Cost. One of the primary benefits of an unlocked cell phone is that it can save you money in the long term. This can be hard to see at first, as the up-front costs are often significantly higher for an unlocked phone than for a comparable locked device.
https://wm15.walmart.com/electronics-resource-center/smartphones/wireless-101/what-is-an-unlocked-cell-phone/
what is an unlocked phone
An unlocked phone is a device that can be used on any carrier that supports that phone.