I don’t understand why voicemail really needs ti be a separate service involving forwarding and such. Couldn’t there be an app that picks up an unanswered call after a timer, plays a greeting, and records the reply? Couldn’t that all be on the device?
Or is there some technical limitation that I just don’t understand? I haven’t found any such app, and all voicemail apps seem to be services that forward calls remotely.
It’s not on your phone, nor is it spyware. You call a number to access carrier voicemail. If you’re worried about them listening to your calls you may as well just not call anyone.