Lock-free phone and verizon crap after just trying their sim card!

[Android Central Question]

I have Galaxy S10e, factory lock-free, with Google Fi. Yesterday my girlfriend had issues with her verizon LTE connection so I put her sim card in my phone to just try it. Verizon installed unbelievable amounts of crappy apps and games, it took me half an hour to remove it. But still the phone acts like formerly verizon-locked. Notifications of "this is not a verizon sim" (no sh..), their logo during startup, even the 4G logo looks somehow different now.
Disabled all the verizon apps (unable to remove completely), reset the APN settings. I will try ADB later, but not sure this will remove the logo and the notifications. And how to block it in the future? How come just a sim card can make such a mess???