Will voicemail work on my unlocked iPhone?
As you either already knew or have quickly discovered, the iPhone's visual voicemail feature only works on approved networks. Though a feature created and supported by the iPhone, visual voicemail is actually a service provided by your wireless carrier.
Does this mean your voicemail icon/button on your iPhone will be "broken" if you're using an unlocked iPhone? Thankfully, no.
What you'll get instead is what you've likely been used to on your previous phone. When voicemails arrive, your voicemail indicator on the iPhone will notify you as it would if visual voicemail was being used (with a red dot icon). Should you click the icon, your iPhone will dial voicemail as you're accustomed to.That's it. Not so bad.