T-Mobile USA offered the cheapest option to own the latest iPhone at US$5 under the company's trade-in plan, amid fierce competition among the top US carriers ahead of Apple's highly anticipated phone launch.
Customers can get a 16 GB iPhone 6s for US$5 per month without upfront payment, under an 18-month lease, in exchange of an iPhone 6, 6 Plus or Samsung's Galaxy Note 5 and Galaxy S6 versions under T-Mobile's latest plan.
They can also get a 16 GB iPhone 6s Plus for US$9 per month under the plan.
Sprint currently offers an iPhone 6s for US$15 per month, under a 22-month lease, with its trade-in plan.
US carriers are also pressured by Apple's own financing scheme for an unlocked iPhone that gives customers the freedom to switch between carriers.
Demand for new iPhones were on pace to beat the 10 million units the previous versions logged in their first weekend last year, Apple said earlier this month.
T-Mobile chief executive John Legere tweeted on Tuesday US time that iPhone 6s preorders were 30 percent higher than a year earlier.
(Reporting by Abhirup Roy in Bengaluru; Editing by Sriraj Kalluvila)