Michael Cohen exits the U.S. Federal Court on April 16, 2018 in Lower Manhattan, New York.
AT&T and the pharmaceutical company Novartis, another Cohen client, said this week that they provided information about their dealings with Trump's lawyer to special counsel Robert Mueller III past year.
Cohen's business dealings, including connections between the shell company and a Russian oligarch, are now under federal investigation.
"To be clear, everything we did was done according to the law and entirely legitimate", Stephenson wrote.
AT&T's head lobbyist, Bob Quinn, who oversaw the hiring of Cohen, is retiring, according to the memo. Mr. Cohen first asked the company to pay $150,000 a month, the people said.
Under AT&T's rules, Quinn had significant leeway to approve the Cohen contract because its $600,000 price tag did not trigger oversight from more senior executives, according to a person familiar with the matter who spoke on the condition of anonymity to discuss internal company practices.
"To all of you who work tirelessly every day to serve customers and represent the brand proudly, thank you".
Michael Avenatti, attorney and spokesperson for adult film star Stormy Daniels, listens to a reporters' question during an interview at The Associated Press, March 21, 2018, in NY.
Avenatti said he was aware of four months of payments to Cohen totaling $200,000.
Initially, it was believed AT&T paid Cohen $200,000. Cohen is also under investigation by prosecutors in NY for possible bank fraud and campaign finance violations.
White House spokeswoman Sarah Huckabee Sanders says that while companies paid President Donald Trump's personal attorney for insight, the president was not influenced. "They didn't get the result they wanted", said Giuliani, Trump's lawyer.
"As an example of the power structure I'm fighting, AT&T is buying Time Warner and thus CNN, a deal we will not approve in my administration because it's too much concentration of power in the hands of too few", Trump said during a speech in Gettysburg, Pennsylvania, in October 2016.
Was Cohen obliged to inform Trump of his corporate clients?
The pharmaceutical giant Novartis acknowledged Wednesday it paid Cohen $1.2 million for services, though the relationship ended after a single meeting.
On Thursday, Novartis Chief Executive Vasant Narasimhan told employees in an email that hiring Mr. Cohen was a mistake and he was frustrated by the arrangement, which was struck under a previous CEO. Last year, AT&T spent almost $17 million on federal lobbying, the third highest among companies.
That firm was Avenue Strategies, a political consulting firm co-founded by former Trump campaign manager Corey Lewandowski and campaign adviser Barry Bennett. In a June 2016 statement he said "it's vital to put our country's well-being ahead of party", called Clinton qualified, and said "the alternative, I fear, would set our nation on a very dark path".
"We didn't engage with them".