One of the hurdles to cross when moving to the Verizon iPhone is voicemail. All of Verizon's other phones use Verizon's voicemail. Apple has their own voicemail system that ties into the iPhone as visual voicemail under the phone app. The product guides that came with the Verizon iPhone warns you of this. Once you activate your iPhone you've then abandoned your Verizon voicemail never to be retrieved again. The other side to this is related to conditional call forwarding. As you move from Verizon's voicemail to Apple's all of that changes as well. Getting it set back up isn't that difficult if you know the codes.
To enable your phone to forward to another voicemail system if unanswered you follow the same steps as any other Verizon phone. Dial *71 followed by the ten digit telephone number. If you're successful you'll hear a series of confirmation beeps. The customer support agent from Verizon told me this wasn't possible because it's not on Verizon's voicemail anymore. However, after giving it a shot yesterday it worked great. To turn off the call forward no answer you dial *73. To do immediate call forwarding use *72.