GoPhone is AT&T’s pay-as-you-go cell phone plan. If you purchased your cell phone as part of this plan but you’re considering switching to some other GSM network provider, then you must unlock your hand-held device first. GoPhone is locked to the AT&T network, and to use it with another SIM card, you have to enter a “subsidy lock code.” If AT&T refuses to give you the code, you may have to purchase it (see Step 4). The typical unlocking method involves entering the code, as received from the website, into a SIM-free phone. You may be instructed to enter the code when the phone is powered on with a SIM card from a different carrier. Tips Writer Bio
