I'm hoping there are some Cell Phone Operator gurus here today.
Would anyone be able to explain how Operators achieve the Visual Voicemail feature on the iPhone (and I assume other newer smart phones)?
If a new cell phone operator that distributed SIM cards wanted to utilise the visual voicemail feature on unlocked iPhone's what services need to be in place to be able to support it?
Is there an open spec or is it completely proprietary?