Switching to NextPBX is easy. When you login to your VoiceNation account, you'll see a popup window telling you about the conversion.
Click the blue "Make the Switch" button, and you'll be sent to a form to fill out your personal information, address and credit card number. Click the "Convert My Services" button at the bottom left, and you're done!
NOTE: If you have live answering as part of your VoiceNation account, you can't convert to NextPBX.