I get several messages a day - especially any time I reboot the Android phone from “128” which is the T-Mobile message number. The message says:
Visual Voicemail Alert” A new version of My Visual Voicemail app is now available. To access your voicemail messages, you will need to download the latest version of the app. Download now: t-mo.co/VMMmvno
Clicking on the link takes you to the Play store to download the app I already have.