Employees using personal phones to connect through corporate phone systems.

Modern VoIP systems allow setting up call-back rules where the system captures caller information. In some contexts, this is also known as "Automatic Callback" or "Ring Again" for busy extensions, as seen on Cisco and Wikipedia .

Call ads (like on Meta) can enable callback requests to secure leads, according to Meta . Call Back | VoIP Phone System Features - Yeastar

High-volume call centers offer this to avoid long hold times, allowing callers to hang up and receive a call back when an agent is free.