GSM cell phones use a SIM (Subscriber Identification Module) card that stores subscriber data. The SIM card is issued by a carrier and provides cell service by activating any phone into which it is inserted.

A locked phone will only recognize a SIM card from a particular carrier. The "lock" is a software setting that keeps the cell phone "loyal" to one carrier.

Unlocked devices are cell phones that recognize SIM cards from any carrier.

If you change the settings for your device you should (these are not included with unlocks), not all phones are able to do data when they are not on original carrier.

Why do Carriers lock phones?

A locked cell phone will not allow users to change phones at their leisure. A locked cell phone benefits only the carrier by keeping a customer using their service.

Some cellular carriers require that you purchase a locked cell phone for the contract period, but will unlock the phone at the time that the contract expires.

Unlocked phones give consumers more control of plans, pricing, and services and make carriers work for you.

Unlocked phones give consumers the freedom to move your SIM card from device to device without signing another carrier contract. This means consumers can easily switch to a different phone whenever they want. This gives them more freedom if their device breaks or is damaged, or if they want to upgrade.

Some unlocked phones are sold directly by the manufacturer, not from the carrier. Sometimes carriers like to alter the phone to fit certain requirements. These locked phones can have alternative carrier software, or have missing pieces of the hardware, such as WiFi or GPS. Unlocked phones sold directly by the manufacturer are un-altered by the carrier, and don’t have any altered software or missing hardware.

Most cellular carriers require that customers sign a contract when they purchase a locked cell phone. Carriers subsidize the price of the phone to make an attractive offer, but require the customer to sign a contract so the lost revenue can be made up over the time period of the contract. However, if the phone is ever broken or lost, the customer must buy another phone, which the carrier usually sells for full-price. Unlocked phones are not subsidized, so they must be sold at full-price, yet the benefit is that the customer does not need to sign a contract or contract extension.

International roaming charges can be quite expensive. Sometimes customer pay a few dollars a minute to make phone calls in foreign countries. Unlocked phones give customers the freedom to travel without paying for roaming. Customers with an unlocked phone can purchase a pre-paid SIM card in the foreign country they are visiting, and pay local rates for local phone calls. To call internationally, the customer can purchase an international phone card with a local access number; thus, the customer is only charged the rate for a local phone call, plus the price of the phone card.

Another alternative is to use the phone as a VoIP device. With VoIP (Voice over IP), the phone makes phone calls over an Wi-Fi spot with VoIP services such as Skype. There may still be a charge, but it is minimal compared to international roaming charges.

Can I use an unlocked phone?

I just bought an unlocked phone; how do I activate it?

I am in the middle of my carrier contract but I want to upgrade my phone.

I purchased this phone when I signed up with my carrier but it doesn’t meet my needs.

I have damaged my phone but am not eligible for an upgrade

I travel internationally but my phone doesn’t.

If I purchase an unlocked phone, are there accessories I need?