Wow, didn't figure I'd be on satelliteguys discussing a voip outage, but I'm in the same boat as everyone else, here.
This has all the markings of a denial-of-service attack against them. If that's the case, then they might be in a heap o' trouble, because if you don't have the kind of infrastructure and IT talent to detect/prevent/recover, it could cost an awful lot of money to bring in the necessary resources to get it fixed in a hurry. And if you don't bring in those resources, that could be the last profitable quarter you see for a very long time.
So the killer about this is that forwarding and voicemail don't even work, because that all depends on phonepower's systems being there to route the calls. Any call to your number gets a busy or some other equally unproductive response. And even if you wanted to arrange some kind of temporary provider, you can't get your number moved until their systems are up.
It's an interesting lesson ... my PhonePower number is just a non-critical residential line, and people can reach me on other numbers. But I guess I'd have to think twice about using a voip provider (*any* voip provider, including AT&T) for mission-critical phone service. The Internet just isn't as reliable as the old AT&T copper network is (or at least was).