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Democrats in the Senate want AT&T's top brass to answer questions about the large sums of money the company paid President Donald Trump's former personal attorney Michael Cohen.

On Monday, Sens. Elizabeth Warren of Massachusetts, Richard Blumenthal of Connecticut, and Ron Wyden of Oregon sent a letter to AT&T CEO Randall Stephenson asking questions about the $600,000 in payments the company made to Cohen last year. The senators questioned the appropriateness of AT&T's dealings with Cohen, given "Mr. Cohen's lack of experience and lack of knowledge about tax reform, antitrust issues, and FCC policy," they wrote in the letter.

"In particular, AT&T had a significant financial interest in key administration decisions, including whether the Department of Justice would contest the proposed merger with Time Warner, whether the Federal Communications Commission would overturn net neutrality rules, and whether the administration would push a tax plan that gave huge breaks to corporations like AT&T," the senators said in the letter.

The company has been in the hot seat since news broke last week that it had made payments to the same shell company, Essential Consultants, that was reportedly used to pay off porn actress Stormy Daniels to keep quiet about an affair she reportedly had with Trump. Michael Avenatti, the attorney for Daniels, whose real name is Stephanie Clifford, shared documents showing AT&T paid the company $200,000. Unnamed sources later told CNBC that the amount could be closer to $600,000.

AT&T confirmed it hired Cohen in early 2017 to get information about the new president and his administration. It hasn't commented on how much was paid to Cohen's firm.

Last week, Stephenson sent a memo to employees apologizing for the mess calling the relationship with Cohen a "big mistake" that has put AT&T "in the headlines for all the wrong reasons."

Still, Stephenson emphasized that the company's dealings with Essential Consultants were all above board and perfectly legal. But he also mentioned that Bob Quinn, head of AT&T's public policy, who had been with the company for more than 30 years, was stepping down immediately after the payments had been made public.

In detailed questions, the three Democrats said they wanted more information from AT&T on its dealings with Essential Consultants. Specifically, they want to know how much AT&T paid Cohen's firm, as well as, which executives were involved in hiring Michael Cohen, and what the decision-making process was like in vetting Cohen's qualifications for the job he was hired to do.

They also asked about a meeting Stephenson and Quinn may have had with president-elect Trump during the transition period after the election.

"Did you, Mr. Quinn, or any other AT&T executives meet with Michael Cohen, Mr. Trump or any other executives of the Trump Organization on January 12, 2017?" the Democrats wrote. "If so, did any of those discussions involve a potential work by, or a contract with, Essential Consultants and Mr. Cohen?"

An AT&T spokesman said, "We are aware of the letter and will respond." But declined any further comment.

News of AT&T's involvement with Cohen comes as the company defends its $85 billion merger with Time Warner in a lawsuit filed by the in US Justice Department. AT&T argues that the deal is critical to enabling the company to compete against tech titans like Google and Netflix, and that the deal doesn't snuff out a competitor. The US government argues that combining a telecom giant, which owns wireless and wired Internet assets, with one of the premiere media properties in the world, would create too powerful a player in the media landscape.

Trump, who has repeatedly called CNN, which is owned by Time Warner, "fake news," said on the campaign trail the day the AT&T-Time Warner deal was announced that he'd try to block the merger if elected.

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