Key Takeaways T-Mobile added fewer new phone customers than anticipated in the first quarter, sending shares lower.The cellphone service provider's CEO also warned that if tariffs raise phone prices,

T-Mobile US (TMUS) is lower despite upbeat first-quarter earnings and revenue, after subscriber growth missed estimates

T-Mobile added fewer wireless subscribers than Wall Street expected in the first quarter as rivals dialed up promotions in a saturating U.S. telecom market, leading to a more than 5% drop in the telecom company's shares after hours.