I remember about 2 years ago, I encountered a very odd “virus”

It was an popup on an iPhone 8 that was unlike any i’ve ever seen before, basically it was like a popup that wanted you to call a number, and it would give you the choice of calling or cancelling. It looked completely identical to Apple system popups, like the “low battery” types.

I’ve never seen anyone find out what is this weird virus. Does anyone here have a clue?