AT&T ended 2011 on a down note, posting a massive, $6.7 billion loss in the fourth quarter due largely to a change in how it accounts for its employee pension benefits and the breakup fee it was required to pay after scrapping its bid to buy T-Mobile USA.

The Dallas telecommunications giant posted a fourth-quarter loss of $6.7 billion, or $1.12 cents a share, reversing a year-earlier profit of $1.1 billion, or 18 cents a share. Excluding the pension costs, breakup fee, and the impairment of its directory asset, the company earned 42 cents a share.