Activist shareholder Elliott Management, which has pressed for big changes at companies including Barnes & Noble and Interpublic Group, said Monday it had taken a stake valued at $3.2 billion in the shares of telecommunication giant AT&T, and urged the company to focus more intently on its operations after a series of big acquisitions and missed opportunities have, in Elliott’s words, “eroded AT&T’s business focus and shareholder value.”

AT&T is grappling with subscriber losses at satellite-distributor DirecTV, which it acquired for $49 billion in 2016 and working to reduce debt after buying the former Time Warner for $85 billion last year.

“What has attracted our attention, as well as the attention of other shareholders — from large institutions to individual AT&T employees – has been the prolonged and substantial underperformance of AT&T as an investment relative to its potential,” Elliott wrote in a letter sent to AT&T Monday. “Over the past ten years, for example, AT&T — a ‘bellwether’ in all senses of the word — has not only failed to keep pace with the broader market, but has actually underperformed by over 150 percentage points.”

The shareholder suggested that AT&T’s move into what it believes are non-core markets – DirecTV and WarnerMedia among them – “has not only contributed directly to its profound share price underperformance, but has also caused distractions that have contributed to the Company’s recent operational underperformance.” Elliott said it takes issue with the exodus of members of the management teams that ran both DirecTV and WarnerMedia and urged AT&T to focus more intently on its core telecommunications business and broaden its leadership team while potentially adding new members to its board of directors and divesting non-core assets.

In a statement, AT&T said it welcomed the chance to consult with its new investor. “Our management team and board of directors maintain a regular and open dialogue with shareholders and will review Elliott Management’s perspectives in the context of the company’s business strategy,” AT&T said. “We look forward to engaging with Elliott. Indeed, many of the actions outlined are ones we are already executing today.”

Elliott was founded in the 1970s by billionaire Paul Singer, and has tended to focus on holdings that deliver high returns while maintaining stable operations. In recent months, it has stepped up its activity, pushing companies ranging from Nielsen to Pernod Ricard to re-examine its businesses.

AT&T’s new shareholder makes its move just days after the telecommunications giant named John Stankey, a longtime AT&T executive who is currently head of WarnerMedia, to be its new chief operating officer, a move that positions him to succeed Randall Stephenson, who is AT&T’s chairman and CEO. Stankey, who has quickly remade WarnerMedia amid an exodus of some of its most senior and well-known executives, will gain oversight of DirecTV and AT&T Communications, and will maintain his role with the company’s entertainment unit.

Shares of AT&T rose $1.03 in early Monday trading, up 2.83% after settling down from an intraday high of $38.07 per share. Volume in the company’s stock was higher-than-normal, standing at more than 74.1 million shares. Average volume is more than 27.9 million shares.