Not the first time I have experienced calls out of Grant, but with a different number. They lead to nowhere, no messages, apparently no purpose other than to bother people. The last one I had out of Grant persisted up to 5x a day for over a year. Callbacks produced a non-existent number according to a phone co. recording.
I, too, have had long-term problems with a number other than this one coming out of Grant, MI. The first Grant, MI caller "didn't exist", if you try to call back. I'm not even fooling with this one which began again in May, 2015. The other one called for over a year. Yes, these are terrorists invading us yet another way.
Yes, they are still at it. I just remember the lucky # "13" at the end of the number on caller id and don't answer it. They have accomplished nothing more than a little gnat.