Randall Stephenson, CEO, admitted that hiring Cohen was a "big mistake" in an employee memo released on Friday morning.
"To be clear, everything we [AT&T] did was done according to the law and entirely legitimate. But the fact is, our past association with Cohen was a serious misjudgment," said Stephenson in the memo.
The memo also states that Bob Quinn, head lobbyist of AT&T, who oversaw the hiring of Cohen, is retiring.
According to a fact sheet provided with the memo, Cohen approached AT&T's External Affairs organization.
"In early 2017, as President Trump was taking office, AT&T hired several consultants to help us understand how the president and his administration might approach a wide range of policy issues important to the company," the fact sheet states.