Wireless provider T-Mobile has promoted two executives to new roles as the company prepares to say goodbye to two others who are retiring.

As part of the shuffle, T-Mobile has promoted John Saw to the role of executive vice president and chief technology officer; he previously served as the executive vice president of advanced and emerging technologies. Ulf Ewaldsson, previously T-Mobile’s chief networking officer, moves up to the role of president of technology. Both promotions took effect this week.

At the same time, T-Mobile is planning to bid farewell to two other key executives: Neville Ray is retiring later this year, at which point he will move to a strategic advisor role with the company. Abdul Saad is also retiring to spend more time with his family; he served as the company’s chief technology officer.

“These leaders contributed so much to the Un-Carrier, delivering what’s recognized as the nation’s best network for customers by independent third parties,” Mike Sievert, T-Mobile’s CEO, said in a statement on Tuesday.

Additionally, T-Mobile’s chief procurement officer Mike Simpson is moving to the finance sector of the company, where he will continue to oversee procurement and supply chain initiatives.