I've just got a phone bill for £400! It turns out that my 16 year-old son has met a girl on the internet who lives a few hundred miles away. As well as talking to her endlessly on on MSN, it now turns out that he's also been phoning her on her mobile. A lot. He has agreed to pay back the money but he doesn't seem to have grasped why this might be a problem. I'm concerned about the very idea of meeting someone online but he tells me it's totally normal and everyone does it. What should I do?