Boost and Virgin are owned by Sprint, which run on the Sprint CDMA network. There's no GSM network for any of them. Verizon is the other carrier with a separate CDMA network. T-Mobile and AT&T each have their own GSM networks.
ETD means that the Eustachian tube is blocked or does not open properly. Air cannot then get into the middle ear. Therefore, the air pressure on the outer side of the eardrum becomes greater than the air pressure in the middle ear. This pushes the eardrum inward.
Eustachian Tubes. When you yawn or swallow, the eustachian tubes open briefly and make the air pressure equal inside and outside the ears (top picture). The eustachian tubes drain fluid from the ears. But if a tube can't open, fluid can get trapped in the middle ear (bottom picture).This creates pressure that can cause ear pain.ustachian Tubes. When you yawn or swallow, the eustachian tubes open briefly and make the air pressure equal inside and outside the ears (top picture). The eustachian tubes drain fluid from the ears. But if a tube can't open, fluid can get trapped in the middle ear (bottom picture).