Very informative Phreznl, but I would make a correction to your summary. Most ROMs that have been around for awhile and have an old 4.1.2 version include Wi-Fi calling, so you can have Wi-Fi calling on non-stock T-Mo ROMs. However you have to find the old file and sometimes that can be very difficult. I know TrickDroid has it (that's what I run), and I think ARHD also has it.
Don't mean to sound rude or anything, just informative to others looking for variation.
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