Business Phone Software

Newer Apps
aircall + Dialpad

Call Center Outbound Sales - talkdesk

Older Software
http://grasshopper.com/ + http://www.ringcentral.ca/

https://www.g2crowd.com/compare/aircall-vs-dialpad
http://www.itqlick.com/Compare/aircall/dialpad
http://www.moblized.com/apps/aircall/compare/switchco