Data data data disappearing again

<p>I've just about had it with vodacom,yesterday I left my house and my "data counter" was on 100MB as my counter was recently reset and I forgot to switgh off my wifi router/modem....I came back in the afternoon and the counter was now sitting on 1.3GB how is that even possible?? I stay alone so no other devices were connected and my wifi is paaword protected so no other connections were made and also my router is set to automatically switch off when there is no activity....when I came back it was off so how can it be that it used 1.2GB by itself???</p>