Very well known scam attempt and there's a few threads on the boards about it.

If you've ever picked up or interacted in any way, they know you have an active number so they keep trying. 

They are very persistent for sure, and a couple of people have come to the boards having fallen for the trap, unfortunately.

Not much to do except keep on blocking them.

It's not an Ebay issue, even though the scammers are claiming to be from "Ebay".