Liberating Your Locked GSM Phone
Wireless carriers sell you "postpaid" contract phones at a considerable discount. The carrier expects to recoup its outlay -- the full price of the equipment -- over the life of the contract that you sign.
Often, it will lock the equipment to its network through a technique that stops the phone working if the SIM (Subscriber Identity Module) card ID and the phone serial number, aka "IMEI number," don't match what's configured. The SIM card is the element that identifies you on the network.
This is done so that you can't use the phone on other networks. SIM locking and the signed contract provide double protection for the carrier, ensuring that it gets its money back.
Radio technology GSM (Global System for Mobile Communications)-driven devices can be unlocked, though, and used on other networks that also use GSM radios.
Unlocking a GSM device allows you to use pay-as-you-go, or prepaid, SIM cards from other carriers. Prepaid accounts can work out cheaper than postpaid accounts, because even though the per-minute charges can be higher, there's no monthly commitment.
How It's Done
The phone equipment is yours -- you've paid for it. You can ask your carrier to unlock the equipment once you believe it has recouped its investment in it. Or, you can unlock it yourself if your carrier is dragging its feet, because requests can take up to two weeks to be completed.
Tip: AT&T, T-Mobile and others use GSM SIM cards. Sprint and Verizon don't use them; they use a different radio technology called "CDMA" (Code Division Multiple Access) that can't be unlocked using these steps.
Remove the battery from the phone, and look for a SIM module. Apple's iPhone SIM card is located in a drawer in the side of the phone. Insert a paperclip in the pinhole and the SIM card will pop out in a tray.
Remove the existing SIM card by sliding it out.
Purchase a pay-as-you-go SIM card from a GSM network like T-Mobile or an MVNO (Mobile Virtual Network Operator) like Locus H2O Wireless, which uses the AT&T network.
T-Mobile SIM cards are cheapest when ordered on the T-Mobile website. H20 SIM cards can be purchased at 7-Eleven and Best Buy stores.
Punch out the new SIM card from the cardholder and insert it into the phone.
See if the phone registers with the new card by looking at the screen. If registration is successful, the network name should appear momentarily on the phone's display. For example, "T-Mobile" should appear.
Tip: H2O requires that you activate service -- by following the steps below -- before inserting the SIM card into the phone.
Activate the SIM card. Look for specific instructions that came with it and follow them. You'll need the 15-digit IMEI number from under the phone's battery or from "Settings" in the phone's software.
Tip: The prepaid carrier usually provides the option of activating via a toll-free number, or website. Pick a plan if prompted -- for example, "Pay by the Day" or "Pay by the Minute." Then add funds to the account using the same tools.
Allow up to two hours for the activation to complete, and attempt a test call. If the call is successful, the phone is ready for use.
Getting Your Carrier to Unlock Your Phone
If you're unable to use a prepaid SIM card from another carrier in your device by following the previous steps, you will need to ask the carrier the device was originally configured to work on to unlock it.
Find the account number, phone number and IMEI number of the device you need to unlock. The IMEI number is under the battery or within "Settings."
Verify that you don't owe the carrier any early termination fee or have any outstanding balance due, and that the phone hasn't been reported lost or stolen.
Then contact the carrier and ask it to unlock the phone. T-Mobile provides a code. Others perform the unlocking remotely on servers.
AT&T requires that you complete any term agreement to unlock its iPhone. T-Mobile will provide an unlock code that it calls a "subsidy unlock" if you've had 40 days of postpaid service and haven't requested an unlock code in 90 days.
Different conditions come into play if you've paid full price for the phone, or are already a prepaid customer. Check with the carrier.
Unlocking the Phone Without a Carrier's Involvement
If the previous steps fail for any reason, you can unlock the phone yourself by paying for an unlock code from an independent vendor. The vendor uses the IMEI number to generate the code. Phones previously reported stolen or lost can't be unlocked like this.
UK-based MVNO Giffgaff provides a Web-based "Unlockapedia" that supplies free, impartial advice about common phones, UK networks and worldwide vendors that unlock phones, including in the U.S.
Scroll down the initial Unlockapedia Web page for a listing of unlocking services, including ratings and user reviews.
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