Sounds like a virtual number (even if temporary) might be helpful. The week of down time seems long, but LNP might be creating something unusual. A virtual number would at least prove/disprove some things (I *think*)

I had an issue once where when I left Vonage to Packet8, I had done LNP. Vonage still had the number in their database and reassigned it to another Vonage customer. That did not interrupt my service but resulted in strange calls.

Hopefully VOIPo can sort it out, but I would reserve blame until they get to the bottom of it.