The hacking victim, Michael Terpin, alleges that AT&T was aware of SIM-swapping attacks targeting its customers but did not act to prevent them
Source: https://cointelegraph.com/news/att-seeks-dismissal-of-200m-in-damages-for-2018-sim-swap-attack
AT&T Seeks Dismissal of $200M in Damages for 2018 SIM-Swap Attack
April 1, 2020
CoinTelegraph