This is a simple guide that explains what it means if your cell phone is unlocked and, how you can tell if it is, as well as some suggestions on how to get your cell phone unlocked. Simply put, if your cell phone is unlocked it can be used with more than one wireless carrier like AT&T and T-Mobile. 

I will start with what is means for a cell phone to be locked.  Many years ago, the wireless carriers such as AT&T and others started a marketing strategy of paying for some of, or all of, the cost of a new cell phone if the customer would commit to a one or two year contract to use their wireless service.  The wireless carriers did not want to pay for the cell phone and later have it used with another carrier, so they got the cell phone manufactures to design the phone to be locked to just their service.  For example, if AT&T paid for the phone, AT&T would lock it so it could only be used on AT&T and not T-Mobile.  This lock is called by several names including: "Sub Lock" or "SPC Lock" or "Sim Lock". 

Now that you know why the cell phones are locked, I will discuss how to tell if your cell phone is locked or unlocked.  First, you must determine if your phone is a GSM phone or a CDMA phone. This is easy to tell, if the phone uses a sim card (a small piece of plastic that you put in the phone, see picture below), 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, Cellular South, QWest, Cricket, Metro PCS and Sprint PCS.  Both CDMA and GSM phones are generally locked, however, only unlocked GSM phones can be easily switched from one carrier to another.  I will address each seperately.

GSM Carriers (AT&T and T-Mobile are the biggest two).  When a GSM phone is unlocked, it will work with any active sim card.  So you can insert an active T-Mobile sim card or an active AT&T card and the phone will make a call.  Now some features of the phone may not work, like the internet browser, if the cell phone is not programmed to the particular carrier, nevertheless, you can make and receive calls.

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

Written by Just Cellular