I think their history of breaches indicates that they are slow to learn from thier mistakes made in securing their customer's PII and as a result I am obtaining my cellular service from a competitor.

Though that competitor has also suffered data breaches, moving to another service makes no logical sense to me since it seems that none of them have a deep commitment to data security since the cost of noncompliance is too low. If meaningful penalties were mandated, something that is unlikely to happen in the current anti-consumer, deregulatory environment, then it would make sense to switch to a provider that has a strong commitment. Otherwise you might as well stay with your current provider.

T-Mobile did get hit annually between 2017-2020 making it appear to a casual observer that perhaps they were just selling the data with their low prices serving as a loss leader and making up the difference by selling everything that they could scrape from customer services annually.

It's a cynical take, I know. It keeps me from switching though.