I don't know what it is, but I get a lot of wrong numbers. On Monday, for example, the phone rang 4 times. 4 wrong numbers. I'd just ignore it, but the boys can't stand to let the phone ring. I've had people calling to buy our apartment, to buy drugs, to ask if we're various kinds of stores, and all sorts of things. An answering machine would be a nice solution, but I honestly don't think people would know what to do if one answered the phone.
So I leave the phone line connected to the computer most of the day. Much quieter.