Cell phone companies started a marketing strategy that was incredibly effective at signing up customers. If you commit to a one or two year contract to use their wireless service, they would provide you with a free or heavily discounted phone.  The wireless carriers feared you would cancel contracts early and take your phone to another carrier, so they managed to get cell phone manufactures to lock the phones. By locking the phones they prevented you from taking it to a different carrier forcing you to buy a new phone if you went elsewhere.  This lock is called by several names including "Sub Lock" or "SPC Lock" or "Sim Lock". 

Is your phone locked or unlocked?

First, determine if your phone is a GSM phone or a CDMA phone. If the phone uses a sim card (a small piece of plastic that you put in the phone, it is GSM, if it doesn't, it is CDMA.  The carriers in the US that are GSM are AT&T, T-Mobile, Suncom, and Rogers ATT.  The CDMA carriers are Verizon, US Cellular, Alltel, QWest, Cricket, MetroPCS and Sprint PCS.  Both CDMA and GSM cell phones are generally locked, however, only unlocked GSM phones can be easily switched from one carrier to another.

GSM Carriers.

When a GSM phone is unlocked, it will work with any active sim card.  So you can insert an active AT&T sim card or an active Cingular (Now also AT&T) card and the phone will function.  Features such as the internet or gps may not function but this depends heavily on the type of phone and the service you have subscribed to, you should be able to make calls.

CDMA Carriers.

CDMA cell phones do not use a sim card and the phone must be programmed to a carrier to work, which generally requires that the phone be programmed by a computer that has the software to program the phone.  If you don't have the software, and it is not readily available, CDMA phones are, for all practical purposes, locked to the carrier they are programmed to.

How to unlock your cell phone.

The United Stated Copyright Office issued a statement that you have a right to unlock your cell phone, in November of 2006. You can find companies that unlock cell phones on eBay and on the internet.  Some companies are able to unlock the phones remotely, meaning if you send them the imei number on the phone, they will send you a code to unlock the phone.  Others require you to send them the phone.  Each model is different, so you will have to search a little to find one.  Charges range from $5.00 to $20.00 depending on the model of the phone. Most local independent cell phone sellers will unlock your phone for about $15, depending on the phone and whether they have the software available.

If you are purchasing a phone on eBay, I would highly recommend purchasing a phone that is unlocked.

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