T-Mobile, once celebrated for rewarding customer loyalty by letting longtime subscribers keep their older, cheaper plans, is about to reverse course in a move that could significantly increase bills for millions of users.

The nation’s third-largest wireless provider confirmed Monday that it will soon force many longtime customers onto newer, more expensive plans — ending a goodwill gesture that had helped it stand out in a competitive market.

The changes target legacy plans, some dating back 15 years, including those under the “T-Mobile One” and “Magenta” branding. Over the next few weeks, affected customers will be automatically moved to the company’s newer “Experience” plans, with phone lines increasing by as much as $6 per month and tablet lines rising by $3.

Customers on older plans will also lose the popular KickBack promotion, which offered a $10 monthly credit for low data usage. For families with multiple lines, the combined impact could add substantially to their monthly bills.

This shift marks a notable departure from T-Mobile’s customer-friendly reputation, which helped it attract millions of subscribers by allowing them to grandfather in older plans. The company says the move is necessary to align with its advanced 5G network and simplify operations, retiring more than 1,000 internal billing codes from legacy systems, including those inherited from Sprint.

However, for loyal customers who stuck with T-Mobile through its growth years, the changes feel like a betrayal of the very loyalty the company once rewarded. The loss of all-inclusive pricing — where advertised rates included taxes and fees — means subscribers will now face additional costs that could push their total bills higher than expected.

As customers weigh their options, including switching to lower-cost carriers like Visible or cable providers, this move highlights the evolving economics of the wireless industry and the challenges even market leaders face in balancing profitability with customer retention.