that T-Mobile subscribers will be sharing some of their personal web and mobile app data with advertisers starting on April 26th. They can avoid this by opting out of the program prior to that date (more on that below). Interestingly, the nation's second largest carrier is requiring that its customers opt-out to avoid sharing data while other firms like Apple will soon prevent ad trackers from siphoning iPhone users' personal data by default.
To prevent getting tracked, T-Mobile customers need to opt-out of a data sharing program by April 26th
says ...