Devices like the evo lte and gs3 could do 3g and lte with voice at the same time because of radio path design. Devices like the htc one m7 and gs4 could no longer do 3g and voice but could still do lte and voice, again due to radio path design. Unfortunately with newer devices like the one m8, gs5, g2, g3(all triband devices) can no longer do 3g and voice or lte and voice simultaneously, again due to radio path design its just not possible. Now when sprint incorporates voice over lte then simultaneous voice and data will be supported.