On October 17th, T-Mobile will begin notifying longtime customers of a forced mobile plan upgrade. If you’re on the Simple Choice, Select Choice, One, Magenta, or Magenta 55 Plus plan, you’ll be migrated to a more expensive package during the November billing cycle. Affected customers can opt out of this automatic upgrade by calling T-Mobile’s Customer Care support line.
Source : T-Mobile Is Pushing Customers to More Expensive Plans, but You Can Opt Out