If you have another method of calling, I suggest calling Customer Care at 855-463-9333. They'll be able to look at your Voice account and see what the issue is. If you're not able to call, you can do a live chat with one of our agents. Click here for a link to start live chat.
Without seeing your account info, this could be as simple as rebooting the modem, or it could be a configuration issue in the back office that needs to be corrected.