I have an Apple iPhone 6 A1586 from the US which was a replacement device from Apple, but the previous handset would've been locked to TMobile (always GSM and never CDMA I believe).
I've inserted a new UK (GSM) SIM into the device and it's telling me the SIM is unsupported. I've checked https://www.icloud.com/activationlock/ and this tells me the device is not locked and can be activated by a new user but I'm unable to do that.
I've wiped the phone and attempted to set it up as a new device but as soon as that new SIM goes into the phone it locks up saying "SIM not supported" but it will still work when I put the old TMobile SIM into it.
Any ideas? Am I missing something here?