T-Mobile CEO Mike Sievert said the telecom giant would use its size and resources to "supercharge" Mint, which is best known for ads starring the actor who is part owner of the smaller company.
T-Mobile said data exposed to theft — based on its investigation to date — did not include passwords or PINs, bank account or credit card information, Social Security numbers or other government IDs.
Names, Social Security numbers and driver's license information were compromised; phone numbers, account numbers, PINs, passwords and financial information were not.
As wireless companies continue to roll out 5G — the next generation of wireless technology — advocates worry this latest high-speed update will widen the digital divide.
A deal years in the making is getting federal regulatory approval to move forward. The $26 billion merger is subject to court approval, and state attorneys general are seeking to block the deal.
"This is a unique opportunity to speed up the deployment of 5G throughout the United States and bring much faster mobile broadband to rural Americans," said chairman Ajit Pai.
The combined company would be called T-Mobile, and have a total value of $146 billion based on current stock prices. The deal, subject to regulatory review, comes after years of failed merger talks.
The Federal Communications Commission says the company had inserted such sounds in "hundreds of millions of calls." But not every FCC commissioner felt the settlement with T-Mobile was penalty enough.
The third- and fourth-largest U.S. wireless carriers had been in talks for a long time but announced Saturday that they could not agree on mutually beneficial terms.