Depending on the device you are using you might not have noticed. I used WireShark on a hotspot that my unlocked IPhone was using and captured the visual voice

Depending on the device you are using you might not have noticed. I used WireShark on a hotspot that my unlocked IPhone was using and captured the visual voicemail blob used by Cricket/AT&T just last week. Also, the SIM card toolkit can be used remotely by your provider. Lookup SimBad exploit