Have to say that is just super weird!! My youngest DD is 8 and she has a couple of close friends but they very occasionally ring, but only on the house phone. I would block their number on your mobile, apparently you can do it! That way they will never be able to get through and eventually give up!!! After school is usually a chaotic time in most households and not everyone has time to sit around and chat! What would a child have to talk about at 6 that needs so many phone calls, is it really that important or are the parents just not interested enough and give their kids the phone to keep them quiet?