Incoming Landline Phone Calls That Just Show "Incoming Call" on Call Display and Aren't Missed Calls

[wireless]

I occasionally receive an incoming call on my Panasonic landline that shows nothing in call display but "Incoming Call". I don't ever answer and the call eventually disappears without ever being subsequently registered by my phone as a missed call. Just before the call drops the phone quickly flashes a "line in use" message. Normally the phone shows "Incoming Call" for a second and then having learned the number involved, flashes that number or say a province name.

Anybody have an idea what these peculiar calls are doing - beyond that they are spam?


More... (https://forum.telus.com/t5/Internet-Home-Phone/Incoming-Landline-Phone-Calls-That-Just-Show-quot-Incoming-Call/m-p/110186#M26300)