Even if you use ATT or Verizon, the article mentions they're also hacked and SMS intercepted often.
The issue is for T-Mobile direct customers, which obviously their internal systems have access to. I see no reason why T-Mobile would have access to users accounts at another company…
"Google says that hackers may have accessed limited customer information via the compromised system, which includes phone numbers, SIM card serial numbers, account status, and mobile service plan data. The system did not contain personal customer information such as names, email addresses, payment card data, government IDs, passwords, or pin numbers."
It's something, but not perfect.
MVNOs do not roam on the carrier, however. The MVNO has a close direct relationship for wholesale access to the network. Roaming is a wholly separate method of access.
Of course you'll still be affected by SIM-swapping etc that just change how your number itself is routed.
And all of them have supposedly been compromised, but T-Mobile is the most compromised.
> While it is true that each of these cybercriminal actors periodically offer SIM-swapping services for other mobile phone providers — including AT&T, Verizon and smaller carriers — those solicitations appear far less frequently in these group chats than T-Mobile swap offers. And when those offers do materialize, they are considerably more expensive.
So the choice is, which one is the least compromised, unfortunately
1. https://en.wikipedia.org/wiki/List_of_United_States_wireless...
technically there are a bunch other small carriers that run their own equipment (not resellers), more than I thought there were: https://en.wikipedia.org/wiki/List_of_United_States_wireless...
https://www.theverge.com/2023/2/28/23617347/dish-cybersecuri...
Verizon and AT&T are the other of the big 3 carriers in the US, and they're not reselling T-Mobile. And all 3 have MNVOs (mobile virtual network operator) that resell and/or combine the networks of the big 3.