T-Mobile has admitted to technical errors during a forced migration of customers to new rate plans, which resulted in some long-time subscribers losing their free-line promotions. The company stated that these errors were unintentional and are being corrected.

Customers complained about the unexpected loss of free lines, which could significantly increase their monthly bills, especially as many were already facing price hikes of up to $6 per line. T-Mobile assured that affected customers would retain their promotions and benefits, with discounts being backdated where necessary.

This issue is part of a larger effort by T-Mobile to simplify its back-end systems by eliminating approximately 1,100 legacy billing codes. The migration aims to offer customers improved network and service experiences, including more premium data and better international coverage, along with a five-year price guarantee for those whose plans are adjusted. The company is also investigating separate reports of incorrect Hulu billing following the migration.