A new study out from Consumer Intelligence Research Partners estimates that between 300,000 and 400,000 total customers who would have otherwise left, wound up staying with T-Mobile USA, Inc. (TMUS) in the wake of the iPhone’s release on that carrier. While T-Mobile certainly owes a debt of gratitude to Apple Inc. (NASDAQ:AAPL) , they would be right in saying, “What took so long.” T-Mobile began offering the iPhone to its customers six years after it was released to AT&T Inc. (NYSE:T), and 18 months after Sprint Nextel Corporation (NYSE:S) began offering the phone.

T-Mobile

Phones activated on T-Mobile

The assertion is based on a small survey of 500 phone activations that occurred between April and June of this year, about 75 of which were on T-Mobile USA, Inc. (TMUS). The company reported losing 199,000 contract customers last quarter and needs this to stop if it wishes to remain the fourth largest wireless carrier in the United States, never mind looking to supplant Sprint Nextel Corporation (NYSE:S) in third place.

Showing the continued use of “unlocked” iPhones in the United States, as many as 22 percent of T-Mobile USA, Inc. (TMUS)’s customers were already using unlocked versions of the iPhone prior to its official launch, according to the report. Since April, that number has swelled to 36 percent now that the phone is being offered, the report said.

T-Mobile phone offering

When T-Mobile first began offering the phone there were numerous reports that T-Mobile stores nationwide were enjoying something they had never seen before outside the store, lines.

Additionally, in a survey of T-Mobile USA, Inc. (TMUS)’s customers found that, among those planning to change devices in the coming year,  28 percent planned to upgrade to an iPhone and remain with T-Mobile.

There is no question that T-Mobile USA, Inc. (TMUS) will never truly compete with its bigger competitors but it can ill afford the customers it loses each quarter. Invariably, those customers do not move to a smaller carrier, but rather a larger one. Additionally, unlike Verizon Communications Inc. (NYSE:VZ) and AT&T Inc. (NYSE:T) who have seen hundreds of thousands of customers leave only to return, T-Mobile does not enjoy that two-way traffic. When customers leave T-Mobile, less than 5 percent return.

T-Mobile has some novel pricing plans that may keep them afloat but there is no question that the popularity of the iPhone 5, is the true reason customers are continuing with the struggling carrier.

I hope someone at T-Mobile USA, Inc. (TMUS) is wise enough to put Apple Inc. (NASDAQ:AAPL) on its Christmas card list.