Can someone school me on iPhones, networks, and unlocking?
I know there are two networks (in the US), CDMA which is used by Sprint, Verizon and US Cellular, and GSM which is used by CDMA. AT&T and T-Mobile. As I understand it, the iPhone is a "world phone" which is to say that technically any given phone from the factory can connect to either network. However, phones are often locked to a single carrier (AT&T, etc) in order to fulfil contract obligations with that carrier. But once the contract is over the phone can be unlocked for use on other networks.
Here's where things start getting murky.
- I have a used iPhone 6 that was sold as an AT&T phone. AT&T has a web tool that allows people to unlock their off-contract phones, so I did that (using the phone's IMEI number, since it's not tied to an AT&T account/phone number). Got the confirmation that it's unlocked, so yay. Does this mean that the phone can be used on any network with any carrier, or just on GSM networks? Can I plug a Verizon SIM card in there and use it on their CDMA network?
- Same question, but flipped. I have a used iPhone 6 that was sold as a Verizon phone. Once Verizon proclaims the phone unlocked, can I use it on any network with any carrier, or just on CDMA networks?
- With AT&T at least, the unlock instructions require me to plug in an AT&T SIM card, then backup the phone, erase it, then restore from backup. But according to their same instructions if I'm not using an AT&T SIM card I need only insert the SIM card from the other carrier and then "follow the setup instructions". Would those "setup instructions" require me to erase the phone too? Would the unlock command (which originated from AT&T) still reach the phone even if it's no longer on AT&T?
- I also have a used iPhone 6 that was sold as a Verizon phone. I was kind of on autopilot and while I was entering the unlock request for the AT&T iPhone, I also entered the unlock request for the Verizon phone -- using AT&T's unlock tool. I realized the error after the fact but was very surprised to discover that AT&T sent me a confirmation email that the Verizon phone was now unlocked. How does THAT work?
- I have a used iPhone 5S that was given to me by an AT&T customer. I went through AT&T's unlock process, got the verification and such so it's officially unlocked. But I can't use the phone on Verizon. Shouldn't I be able to? I thought the 5S was also a "world phone". After some Googling it seems that there are some iPhones (or at least iPhone 5's) which can't be carrier-unlocked and this iPhone 5S is one of them. What's up with THAT? What other iPhones are similarly carrier- or network-locked?
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