The deal values Atento at about 6.4 times its operating income before depreciation and amortization of €161 million for 2011 and about 0.58 times sales of €1.8 billion. The enterprise value includes €175 million of net debt and a €110 million deferred payment.

Bain, the PE shop co-founded by Presidential candidate Mitt Romney, is proving itself a big believer in the prospects for call centers. Its acquisition of Atento, the world's No. 2 call center operator, comes just three months after the Boston-based group paid about $1 billion for a 30% stake in the world's biggest call center operator, Genpact Ltd. In 2009, Bain paid ¥93.5 billion ($1.2 billion) to buy Japanese call center operator Bellsystem24 Inc. from Citigroup Inc.

Telefónica's CEO Cesar Alierta is selling assets, and recently scrapped a dividend payment, to pay down his company's debts amid an expected decline in Ebitda resulting from rising interest rates on its €58 billion of debt and increased taxes. Standard & Poor's on Oct. 3 said that Telefónica's credit rating of BBB was on negative watch, noting that the company had €7 billion to €8 billion of long-term debt maturing annually through to 2015.

"We are aware of management's intention to execute additional disposals in 2013 but we have not factored them into our forecasts at this stage, given execution risks and uncertain timing and proceeds," S&P said in a note.

Telefónica had previously considered spinning Atento off through an IPO but abandoned the plan in 2011. Madrid-headquartered Atento is the largest call center operator in Latin America and makes about 54% of its revenues in Brazil. It operates 165 call centers in 17 countries and has a workforce of about 156,000 people.

"This transaction is part of the policy of proactive management of the portfolio of assets of the company and the initiatives to increase Telefónica's financial flexibility," the Madrid-based company said.

Telefónica last month paid itself €4.3 billion in the form of a special dividend from its German unit Telefónica Deutschland Holding AG. The German business is being prepared for an IPO that is expected to result in the sale of between 20% and 30% stake. The sale, which is scheduled for before the end of the year, is expected to raise about €1.5 billion for the Spanish parent and value the German business at about €7.5 billion.

Bain's acquisition of Atento should conclude before the end of the year.

Shares in Telefónica traded Friday Morning at €10.28, up less than 1% on their Thursday closing price.