WiFi Calling: is the ability to receive telephone calls and send or receive SMS messages on a device that does not have cellular capability. In essence it turns your Mac, iPad, iPod, etc into an additional receiver on a linked iPhone’s account and counts against any limits on the iPhone’s account. When someone calls the linked iPhone all of the linked devices ring and the incoming call can be taken on any of the devices. SMS messages are likewise received on all of the linked devices as well. It can be convenient or annoying. (Imagine the clamor in my office when someone calls my iPhone and the iPhone, iPad, Mac, and server all ring at the same time. I wish Apple would add a location feature to WiFi calling that would allow the user to select which WiFi calling enabled device would ring when two or more are in immediate proximity.)
As to the blocking, a question would be how a NEW iPhone that was discontinued five years ago got into the market? I can think of several semi-licit or outright illicit channels that could have resulted in your new iPhone being on a list of suspect devices. It is at least equally possible more likely perfectly legitimate and the blockage the result of a coincidental action.
