While T-Mobile executives are reluctant to credit the failed merger with AT&T as the source of the firm’s aggressive new pricing strategy, they admit that they see themselves as disrupters in the market. “We want to identify every pain point for consumers in this industry and eliminate them all,” said Michael Katz, T-Mobile’s vice president for marketing.

In the last year, T-Mobile has dropped the traditional two-year contract from its lineup; now its plans come without customer lock-in. It has also dropped early termination fees, overage charges and other extra strings that carriers apply to keep you in line. The carrier now allows customers to text and use the Web while traveling in 100 countries at no extra charge. T-Mobile has also offered to pay off the early-termination fees its new customers might incur with their old carriers when switching. Most important, it has unbundled the price of a phone from the price of wireless service. Now, you can pay a separate amount for each piece. This means that if you decide against immediately upgrading when you finish paying off your phone, your monthly bill might — astonishingly — go down.

Former F.C.C. officials say this is exactly what the agency hoped for when, in 2011, it weighed in against AT&T’s plan to purchase T-Mobile. As the agency’s staff explained in a lengthy report, regulators feared that shrinking the four major carriers to three would give providers an incentive to raise prices. Instead, regulators saw an elegant escape hatch for T-Mobile. If AT&T was forced to call off the deal, it would owe T-Mobile a breakup fee worth at least $3 billion in cash, plus an additional $1 billion in rights to wireless spectrum. The money and spectrum would allow T-Mobile to build out its network infrastructure, making it more attractive to new users. Given the right leadership, regulators hoped the fourth-place carrier could play a spoiler’s role in the marketplace. By aggressively courting new users, T-Mobile would act as an agitator prompting change across the industry.

And that’s what has happened. After the merger fell apart, T-Mobile began to invest heavily in its network; its LTE broadband area now reaches 200 million people and its access speeds have been found to be faster than those of its larger rivals. The firm’s real innovation began last March, though, when it announced its Simple Choice plan, which offered two unusual features. First, there was no contract lock-in; if you found a better deal on some other network a few months after signing up, you were free to leave. Second, the advertised prices were for network access alone, and did not include a smartphone. If you wanted a smartphone, T-Mobile would sell you one at full price, splitting the payments over two years. A top-of-the-line phone, like the iPhone 5S, sells for about $650, which is about $27 a month for 24 months.