T-Mobile's smartphone sales have increased to the highest point yet over the last year, according to a new report from Kantar Worldpanel published on Monday. The carrier sold 13.2 percent of all U.S. smartphones during a 3-month period ending in August. That figure represents a slight but noticeable 1.1 percent bump over the same time last year – when the carrier's smartphones sales were falling as it lagged behind with its LTE roll-out. The iPhone was T-Mobile's hottest smartphone and made up 17.1 percent of all smartphone sales., Kantar said.

Verizon still sells the most smartphones in the United States, with a 37.1 percent market share, followed by AT&T with a 21.7-percent share and Sprint with a 14.6-percent share of all smartphones sold in the United States. The increase in T-Mobile's growing share suggests that its new "Uncarrier" plans, which allow you to buy a device with a low down-payment and subsequent monthly payments, are paying off.

Kantar Worldpanel also said that Android has a 55.1-percent share of the U.S. smartphone OS market, up from July, followed by iOS with a 39.3 percent share,  Windows with a 3 percent share and BlackBerry, which is now down to just 1.8 percent of all smartphone sales.