A couple of companies are looking to buy your VoIP base.
One is VoIP Your Life LLC. "WE'RE BUYING small, residential and\or business VoIP customer bases (preferably, US-based). Interested in divesting? Kindly message me and we can arrange for a time to discuss." [from LinkedIn BroadWorks Group]
Flat Planet Phone Company is looking for VoIP companies in the US with up to 10,000 extensions for sale. Terms depend on the deal.