Activist hedge fund Elliott Management revealed on Monday that it had taken a massive position in AT&T (T), saying the telecom giant can see its stock double by the end of 2021 by undertaking big management changes.

In a letter to the board, Elliott Management says it owns $3.2 billion worth of AT&T, one of the firm’s largest positions in its history. It has a price target of $60 by the end of 2021.

While calling the company’s underperformance in the last decade "severe and disappointing,” the hedge fund added that by undertaking structural reform, the company has a shot at real growth.

Elliott’s "Activating AT&T Plan" includes the company "divesting non-core assets; reducing operational inefficiency; instituting capital discipline,” as well as shedding debt and bolstering its leadership and oversight, according to the letter.

“Elliott believes that through readily achievable initiatives [like] increased strategic focus, improved operational efficiency, a formal capital allocation framework, and enhanced leadership and oversight” the stock could effectively double in two years.

That move represents “a rare opportunity for any company, let alone one of the world’s largest,” it added.

Shares of AT&T jumped more than 3% in early trading, last changing hands near $37 from Friday’s close.

‘Distractions’, and an underperforming stock

In the letter, Elliott outlined how AT&T has underperformed over the last decade, specifically pointing to its dealmaking strategy as the main culprit.

Some of the "questionable” mergers and acquisitions (M&A) Elliott highlighted include blockbuster purchases of Time Warner in 2016 and DirecTV in 2014, and the attempt to buy T-Mobile. The latter was something Elliott called "the most damaging deal was the one not done.”

Elliott called AT&T an "outlier" when it comes to its M&A strategy, noting that the company has sought to assemble conglomerates.

"We firmly believe that AT&T’s M&A strategy 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," the letter said.

The firm listed a litany of other gripes against AT&T’s management that contributed to low shareholder value, and a “prolonged and substantial underperformance of AT&T as an investment relative to its potential," Elliott wrote.

"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,” Elliott added.