Voicemails being "Deposited into text"

Pardon my ignorance but I don't know what the VM app is. By the name I would expect it to be Voicemail but I don't know of any such app. I have the T-Mobile app which is in pink with a large T on it.  That's the one I've been using to try to turn off the T-Mobile Voicemail to Text option. I've looked in the App Store for some other T-Mobile app which deals with voicemail and I can't find one. Other than that there is Apple's Phone app which has Apple's voicemail in it but I wouldn't consider it a voicemail app - it's a phone app that also has voicemail. Is there some other app I'm missing? Also, in the T-Mobile app, at the top level, top right, there are not 3 dots so I don't expect you mean that app.