T-Mobile announced that it will offer its first 5G-enabled smartphone, the Samsung Galaxy S10 5G. The device will be available in select cities starting June 28, but why would anyone by a 5G smartphone if there's no 5G network to pair it with. No worries, as T-Mobile has just confirmed that it will fire up 5G in six cities in the United States on the same day the Galaxy S10 5G goes on sale, June 28.