The only option I have seen here so far for organic outreach by phone is @Dan Canfield's

Byron

VA offering. Especially for thousands of calls. Does anyone know of other genuine options for truly awesome outbound calling agents, transparently branded, who fit into existing outreach teams/campaigns naturally?

Connect and Sell is the #1 predictive dialler. I've used them in the past on a service basis - not sure if they still offer this.