It's a solved problem. VoIP plus leased trunk lines by the a telco in the market you want to work at. You are limited to fixed set of numbers and you are "local" in the market you want to work at.

That we can do better now isn't important to why something existed to be grandfathered-in in the first place.

Call centres were getting outsourced before e.g. Skype was a twinkle in the eyes of Priit Kasesalu and Jaan Tallinn.