August 28, customers can light up an eSIM with a T-Mobile postpaid plan – to open new ways of using an eSIM-equipped device by adding a second line on the same device. eSIM is great for people who want to use both work and personal numbers on a single smartphone, set up a phone with an international carrier for extended stays outside the U.S. or just get rid of that physical SIM card. Plus, AT&T, Sprint and Verizon customers can get T-Mobile on their existing smartphone.