4. AT&T Voice HD


If you’re one of the few using a smartphone to actually make phone calls, better sound quality is on the way. AT&T is rolling out high-definition calls over LTE this month, beating Verizon to the punch.

Meanwhile, T-Mobile’s HD voice service has been running for a while now, but so far you can only enjoy its sweet sound quality with other T-Mobile subscribers on certain phones.

via The New York Times