Cell phone picture

I have just had something really disturbing happen. I'll begin by saying that my 2 older teens are on trips right now. I just received a picture of a female anatomy with some photoshop work done to it. Not amusing, although a teenage boy would think so. The number was a local cell phone. So my first thought was that someone got my # from my kids phone, or maybe they themselves did it with someone else's phone. I was livid. Of course having teens I suspected them. I texted one to see if he knew anything, but then I called the number back without thinking much. I thought if it was a kids voice I was going to push them until I found out who had done what. Guess what- it was a man. An older man. I asked him what he meant by sending me this, and told him my teens almost got in huge trouble over it. If I hadn't called it I would have gone on thinking one of them had something to do with it. He said it was a mistake, he sent it, but it was meant for another number. So now my concern is- how many of us give our kids cell phones? How many of us feel the need for our young teens to have a phone in their hands so we can know where they are, and they can call for help, and a ride. What if this picture came up on my younger son's screen???? Is there anyone to report this to? If it was online I would do my best to try to report it to someone who could police such things. But what about a cell phone picture?? This was not a soft core picture. This was pretty obscene. The man just sounded sorry, and sheepish, and I hung up on him. If I ever have any more contact from that # to my phone I will take some sort of action.