It seems AT&T is a target. I have AT&T and this morning I got that text exactly with the wording about it's an invalid number please redial blah blah. I texted back to it "who are you? you show up as unknown " . This happened for the first time today (19 Dec 2015). I have an iPhone as well. It would be interesting to compare area codes with the dates people started getting these texts and calls. Wonder if it is systematic targeting of area codes one by one, or just randomly choosing numbers to text and or call? I am 651 area code