T-Mobile says Mike Sievert will become CEO in May, following the end of John Legere’s contract.

The company said Monday that the move is part of its succession plan.

Legere will remain with the company as a board member. Sievert, who has worked with Legere for the past seven years, currently serves as president, chief operating officer and a director.

“John Legere has had an enormously successful run as CEO. As the architect of the Un-carrier strategy and the company’s complete transformation, John has put T-Mobile US in an incredibly strong position. I have the highest respect for his performance as a manager and as a friend, I am very grateful to him for the time together,” said Tim Höttges, Deutsche Telekom CEO, and Chairman of the Board of T-Mobile US in a statement.

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Legere announced in a series of tweets that he would be stepping down as CEO on May 1, 2020. He said the move had been under development for a long time. 

"You've heard me joke that he's 'my son,' but in reality since I hired him in 2012, @SievertMike's been my mentee, my secret weapon and my friend," he wrote. "In our time we've launched 16 #uncarrier movies, shifted an archaic industry for consumers and weaked havoc on the competition." 

"I'm telling you, @SievertMike is absolutely the right choice to be the next CEO of @TMobile," he added in another tweet. "I know he'll take what we've done for the past 7 years and superchargeit!"

Sievert also tweeted about the announcement, saying he "could not be more excited to continue to follow in @JohnLegere's footsteps and expand this mission as CEO.