Unfortunately, since Jon wished that no one could hear his voice, no one could hear the wish that was made. And since the stone could only affect people within a few miles of it, the wish he made over the radio would only affect people in Jon's town and a bit of the outskirts.
So, in other words, it wasn't any different than if Jon just said the wish to himself ... except that he couldn't hear his own voice, since that was part of his previous wish. The change would happen, but no one would think it was strange or out of the ordinary, and thanks to Jon's "no one hears my voice" wish, Jon wouldn't find it out of the ordinary either. As far as he knew now, men (at least in his town, for some reason) had always had breasts.
Jon tried to remember what he said over the radio, but the memory totally escaped him. He shrugged, which caused his B-cup breasts to jiggle a bit. Unknown to him, he acquired them from his Goth sister Zoe, who was in her bedroom next door talking to her friends Athena and Zelda. Really, he could have gotten breasts from any one of them, but the moment that he made the wish (that he didn't hear), Zoe was the closest to him.
It always puzzled him how his breasts were always several shades lighter in skin tone than the rest of his body, but he just supposed that he needed more sun.
He turned up his radio, listening to the song that was played next, then he got ready for work ...
