T-Mobile added 1.6 million net new customers, including 1 million postpaid subscribers, who pay monthly bills and are generally the most sought-after customers for wireless carriers. Of these new postpaid subscribers, 686,000 were phone activations, which led the wireless industry for the 18th consecutive quarter.  

T-Mobile also strengthened its retention of existing customers; the company's branded postpaid phone churn rate improved 15 basis points to 0.95% in the second quarter.  

CEO John Legere said in a press release: "T-Mobile just recorded its best Q2 in company history. That means 21 quarters with over 1 million net adds, record-high service revenues, industry-leading postpaid phone net additions, and record-low postpaid phone churn."  

These subscriber gains drove a 3.5% increase in revenue, to $10.6 billion. In turn, EBITDAOpens a New Window. -- adjusted to exclude stock-based compensation and certain other items -- rose 7.3% to $3.2 billion. Operating cash flow, meanwhile, leaped 14% to $1.3 billion.  

All told, net income, which benefited from lower interest expense and a lower effective tax rate due to tax reform, surged 34.6% to $782 million. And earnings per share, boosted by stock buybacks, soared 37.3% to $0.92.