The surprise move comes as speculation swirls around the possibility that Doctors was a leading player to become the next CEO of WeWork – although Doctors shot down reports that he was looking to take that job.
Sprint is controlled by Japanese investment giant SoftBank, which also has a controlling interest in WeWork.
WeWork is looking for a new CEO after Adam Neumann was forced out when the company was forced to scrape its original offer plans due to concerns about the company's management and loss management.
But Doctors said during a conference call with analysts Monday that he had never had discussions with WeWork, and added that rumors that he was leaving made things "difficult" since he was already about to expel a T-Mobile's success plan.
Investors took the news of Doctors' steps down. A-shares of T-Mobile were down just a little Monday while Sprint's share rose almost 1
T-Mobile was not concerned about states' legal challenge to Sprint agreement
Doctors said that in the last few months as CEO, he plans to focus on making sure the agreement with Sprint is terminated. The merger has received government approval from the US Federal Communications Commission and the Department of Justice. But a group of attorneys general from several states are still trying to block the merger. A trial will begin in December.
Sievert said during the conference call that he was not too concerned about the possibility of the Sprint agreement loosening.
"We are planning to win, as you know, and we are becoming increasingly confident that we are getting closer to the trial," he said, adding that T-Mobile's main focus "is to get to this deal and build this new company , which unlocks this huge network capacity and the massive synergies that result from that capacity expansion. "
Doctors, who are often seen wearing a magenta T-Mobile t-shirt, often create fun at these bigger rivals – and he said ID Monday that would not change.
"This transition is more than 5 months away, so you will still have plenty of time and opportunity to hear me take pictures of the competition," he said during the interview. "So don't get too excited, AT&T, Verizon, Comcast and Charter."
Sievert seems to be intensely imitating the Army's brash style as well.
During the conversation, Sievert promised to continue to refer to a combined T-Mobile and Sprint as "un-carrier" – a term Doctors coined to describe what he thought was T-Mobile's more customer-friendly style business.
"Our lower costs and larger scale will simply allow us to abandon the un-carrier strategy and bring even more competition to this market," Sievert said, adding that AT&T and Verizon "have no idea what is about to hit them and customers are going to be winners. "
Weak praise for Verizon
But Doctors had some kind words for Verizon, who is partnering with Disney to offer the House of Muse's new Disney + streaming service for free for many Verizon mobile phones and Fio's internet and 196 subscribers.
"Disney + looks like it's been a huge success out of the gate. And there are some good assets there," Doctors said.
But in true Army style, he quickly called Verizon's partnership to be a copycat move to the deal T-Mobile has with Netflix that lets T-Mobile subscribers get Netflix for free.
"I think Disney + is an exciting platform. I do not deny it, but Verizons offers absolute pale in comparison to what T-Mobile offers," Doctors said, adding that T-Mobile may consider other partnerships but did not some plans to create their own content like AT&T, Verizon and Comcast do.
"We are not designing a media company," Legere said.