I was a little surprised when I went to add LTE Voice (or HD voice as a free feature) to my 7+ that I got from the Apple Upgrade program unlocked and it didn't work. I was told by a Verizon representative that this "feature" is only available to customers who get their phones from Verizon. They claim there's "software" that makes this possible. This perprlexed me. Wouldn't my unlocked phone be the exact same I got from Verizon? The model number is exactly the same. Do other carriers do something similar? It's enough to make me want to go to ATT.