Shares jumped 3.6 percent to $46.01 in premarket trading.

In the quarter, Verizon added 614,000 subscribers who pay a monthly bill, including tablet customers, compared to an increase of 615,000 in the year-earlier period. The additions were higher than the JPMorgan estimate of 115,000 and consensus expectations of 70,000, JPMorgan analysts said in a research note on Thursday.

Verizon has been competing for customers with smaller rivals T-Mobile US Inc and Sprint Corp in a saturated U.S. market for wireless service as most consumers already have cell phones.

In February, Verizon reintroduced an unlimited data plan for the first time in more than five years. Since then, other carriers have launched aggressive promotions. Sprint said in June that it was offering free unlimited data, talk and text for a year to consumers who bring their own devices in a promotion aimed at Verizon subscribers.

The company added 358,000 phone-only subscribers, compared with 86,000 net additions a year ago.

Verizon's unlimited plan, priced at $80 a month for a single line, is more expensive than competing plans. Chief Financial Officer Matthew Ellis said Thursday's post-earnings conference call that "even with the price premium we have, it shows that customers value the high-quality network experience that we deliver."

Churn, or the rate of customer defections for subscribers paying a monthly bill, was flat at 0.94 percent from the year-earlier period, and lower than analysts' estimates of 1.1 percent, according to JPMorgan.

Jonathan Chaplin, an analyst at New Street Research, called the subscriber numbers "very strong," but added that "we remain cautious on Verizon equity given what we regard as unsustainable margins and returns in a competitive market."

Net income attributable to Verizon rose to $4.36 billion, or $1.07 per share, in the second quarter, from $702 million, or 17 cents per share, a year earlier.

Excluding items, earnings were 96 cents per share.

Total operating revenue edged up to $30.55 billion from $30.53 billion a year earlier.

Analysts expected adjusted earnings per share of 96 cents on revenue of $29.91 billion, according to Thomson Reuters I/B/E/S.

The latest quarter included a gain from the sale of data centers and lower expenses. Earnings in the year-earlier period were also hurt by a strike in the wireline business.