I'm hoping for some assistance with some Verizon SIII Minis that I've acquired. I'm trying to get them working on carriers other than Verizon - be it T-Mobile, Straight Talk, or any other GSM-based carrier. Before getting involved in this, I was under the impression that all Verizon LTE devices were factory unlocked and could be used on other carriers without any issue. However, I'm finding that the S3 Mini may be the exception to this (although I’m aware they are not locked, it seems something else is preventing them from accessing the Verizon network).

To start, the phones in question are running a stock Verizon version of Android 4.4.2. Inserting a T-Mobile SIM does not result in the phone detecting a network. I’m aware that there may be incompatibilities with certain bands that T-Mobile offers, but I believe the phones should be able to pick up 2G or 3G service. I've done fairly extensive research online and have reviewed a number of suggestions, including:

-Disabling the setup assist (if setup assistant runs it will indicate an invalid SIM)
-Switching the phone from CDMA to ‘Global’ Mode: The option described does not exist in the menu
-Changing/adding a new APN - the option to add a new APN is greyed out
-Dialing various codes - none seemed to be effective

Has anyone successfully gotten a Verizon S3 Mini to run on another network without rooting it? If so, I’d appreciate any suggestions how I can get these phones working. Thanks in advance!