Few executives have had such an impact on their companies as T-Mobile’s CEO John Legere. During his time with the company, T-Mobile more than doubled its subscriber base, went from fourth to third place in the country and negotiated the pending acquisition of Sprint.

Now, according to a company press release, Legere will step down as CEO when his contract expires on April 30, 2020, handing the reins to current COO Mike Sievert.

“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.

Legere will remain on T-Mobile’s Board after stepping down. In the meantime, his focus will be on concluding the Sprint acquisition.

“I hired Mike in 2012 and I have great confidence in him. I have mentored him as he took on increasingly broad responsibilities, and he is absolutely the right choice as T-Mobile’s next CEO,” said Legere. “Mike is well prepared to lead T-Mobile into the future. He has a deep understanding of where T-Mobile has been and where it needs to go to remain the most innovative company in the industry. I am extremely proud of the culture and enthusiasm we have built around challenging the status quo and our ongoing commitment to putting customers first. Together, these attributes have distinguished T-Mobile in the marketplace and on Wall Street, giving us a powerful business advantage that is instilled throughout every level of T-Mobile. I am confident it will thrive under Mike’s leadership.

“In the months ahead, my focus will be on ensuring a smooth leadership transition and continuing to work closely with the Board and Mike to complete the Sprint transaction. This merger will create the New T-Mobile – a company that is uniquely positioned to continue disrupting the wireless category – and beyond. This marks the beginning of a dynamic new chapter for T-Mobile.”