The fourth quarter of 2010 — the busy holiday quarter — was not all that fruitful for the U.S.’s forth largest wireless provider. In an earnings call today, T-Mobile posted a nearly flat revenue number — $4.69 billion in Q4 2010 versus $4.71 billion in Q3 of 2010, and $4.65 billion in Q4 of 2009 — and less than stellar customer retention numbers. T-Mo saw net losses of 318,000 customers in Q4, along with a churn rate rising from 3.4% in Q3 to 3.6%. One bright spot on the company’s balance sheet is the 25% jump in “data services revenue” year-over-year.

“I am pleased with the increase in smartphone adoption and our ongoing improvement in data ARPU. Data growth in the U.S. mobile market continues to accelerate and with the largest 4G network T-Mobile USA is well-positioned to differentiate itself and grow consumer usage,” said René Obermann, CEO of Deutsche Telekom. “We are not satisfied with contract churn, but we expect that the measures presented at the T-Mobile USA Investor Day in January will lead to improvements in 2011.”

T-Mobile’s full press release is after the break.