T-Mobile has an extra surprise in store: it's rolling out HD Voice calling nationwide, and claims to be the first US carrier with the achievement. Those who have a smartphone capable of the feat, such as the HTC One S, Nokia Astound or Samsung Galaxy S III, can get both higher quality calls and fewer noticeable distractions in the background. Upgraded quality is available as of today, which should help us get some extra mileage out of that new unlimited plan.