I know that several years ago, some iPhones had CDMA and others GSM, and others yet had both, depending on which carrier the phones were meant to work with.
But I read somewhere that nowadays, all of them come with extensive network compatibility. AT&T told me that their phones are locked but can be unlocked once fully paid off. So it sounds like there is a software lock but perhaps the hardware is universal.
I am looking to buy a T-Mobile phone, get it unlocked, and then switch immediately to using another carrier.
Are all iPhones the same now, in terms of communication hardware/software?