New T-Mobile CEO: Sprint Users Can Still Keep Plans After

"No one's plan will change," Sievert said. "Today we completed our merger and everybody has the same plan today they had yesterday.

"A long-standing policy at T-Mobile is that people get to keep what they have," he said, adding that the company will rollout new offers in the "coming weeks" under the new, unified T-Mobile brand that are "highly attractive in the marketplace."

"We know what kind of offers our customers are looking for."

With T-Mobile closing the Sprint deal after two long years, Sievert took over the CEO position from John Legere on Wednesday, one month ahead of a previously announced transition on May 1.

Sprint users will be able to tap into T-Mobile's 4G LTE network today without having to do anything on their phone, with Sievert noting that the company is using roaming for LTE to "immediately add both coverage and capacity" for Sprint customers.

For Sprint's 5G devices, a software update is coming to enable them to connect to T-Mobile's 5G networks.

T-Mobile is also already deploying the newly acquired Sprint 5G spectrum (known as midband), which provides faster speeds than T-Mobile's low-band 5G network while still working indoors.

Neville Ray, T-Mobile's president of technology, says that Philadelphia is the first city to go live, with others set to be turned on "rapidly" in the coming weeks. Every T-Mobile 5G device that the carrier has launched will be able to tap into the midband 5G once it's deployed.