T-Mobile US Inc. /zigman2/quotes/204659678/composite TMUS -0.76% shares rose in the extended session Wednesday after the telecom announced it added the most customers ever within a year. The company said it added 1.6 million postpaid customers in the fourth quarter for a total of 5.5 million postpaid customers in 2020, the most in T-Mobile’s history, according to preliminary numbers. The rollout of the 5G wireless standard helped boost numbers, the company said. T-Mobile said its extended-range 5G service covers 280 million potential customers and that it’s ultra-capacity 5G services covers 106 million with nationwide service expected by the end of the year. T-Mobile shares rose 2.1% after hours, following a 0.2% decline in the regular session to close at $131.53.