I'm working on this concept since 2013 to enable calls to call center agents through websites & mobile apps (& other channels, even from an FB page or eBrochures).
No more expensive and limited Toll free numbers setup (TFN), no more landlines or DIDs (direct inward dialing).. all the caller needs to talk to the agents is an internet & by clicking a button on a website/app for free. and, no more long distance charges nor use of phone loads/credits..