You can of course use the voicemail feature! I just ported over from Verizon myself and I had to go to my iphones phone app, click on voicemail, and set it up once again. After i set it up it works fine!
Just wanted to check in here to see how things are going. Are you still having issues with this? If so, please contact us so we can take a closer look at your account to ensure your voicemail is provisioned correctly.