I'm not really familiar with the iPhone/Blackberry visual voicemail. This may or may not be helpful.
If I read you correctly, you spoke to Customer Care to turn on the voicemail feature, but haven't actually called your voicemailbox yet. There's a button on your visual voicemail page to set it up, but the button is disabled.
What happens if you dial voicemail? There should be a setup involved, beyond Care just turning it on. If you dial voicemail and set up that part of it, does the button to set up visual voicemail in the phone become enabled?
Also, the visual voicemail you should have with an iPhone or Blackberry is a different feature than the normal basic voicemail everyone else has. You may want to confirm the feature that was added really was visual voicemail.
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