That phone then functions on AT&T’s network, but if you try to place a T-Mobile SIM card into the phone and switch to T-Mobile’s network, the phone will reject the T-Mobile SIM card. Carriers “lock” phones to make them only function on that carrier’s network.įor example, let’s say you walk into AT&T and pick up any smartphone on contract. However, there are also artificial barriers. The CDMA/GSM difference is a legitimate technical barrier to moving phones between carriers. Before you consider unlocking a phone and taking it to another carrier, ensure that your phone will actually be capable of functioning on that carrier’s network. Luckily, most of the world has chosen the less-restrictive GSM standard. These are incompatible with each other, which means that you can’t unlock a CDMA phone purchased on Verizon and take it to AT&T’s GSM network, or vice versa.ĬDMA is also a more restrictive type of network-while you can unlock an AT&T phone and take it to T-Mobile, you can’t unlock a Verizon phone and take it to Sprint, as Sprint’s CDMA network will reject the phone. For example, in the USA, AT&T and T-Mobile use the GSM wireless standard, while Verizon and Sprint use the CDMA wireless standard.

Unlocking Won’t Make Phones Completely Portableįirst, it’s important to bear in mind that phones won’t always be capable of working on another carrier even after they’re unlocked.

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