T-Mobile Admits Storing Passwords in Plaintext
twitter.com
twitter.com
https://twitter.com/tmobileat/status/981418339653300224
For clarity, this is T-Mobile Austria.
Considering that there was a hack at Sony for example that exposed plaintext passwords as well via SQL injection (among many other things of this nature) they can't claim ignorance of the problem.
It was a yuuuuuuge shitstorm for Sony at the time.