Nothing mentioned on the box, webpage, or literature, so I gave it a shot. Also clarying that not all HDvoice phones have voice over LTE, for example blackberry z10, lumia 635, and others all drop to hspa when you make a call. I made a call on the lumia 640 I just picked up from my local Walmart and it stayed on lte throughout the call. It seems this will be the norm for band 12 phones, including the budget ones, as the galaxy avant also has the feature. Although it was an incredible wait, thank you to tmobile for bringing us the first volte windows phone.