Integrity of Vodacom's billing system

I have been with Vodacom since its inception but I have noticed that they add on items to your contract and you always end up paying more than you signed up for. I recently signed a contract which should cost R307.86 pm but all of a sudden I have items added and now I must pay R393.84pm. You just cant find a human to talk to that can help you regarding removing these add on's even though I have tried 4 x already. Its only a small amount of money but it the principal and now I'm questioning the integrity of Vodacom because not only do most people not check/or worry about this small amount that has been added on but you eventually give up and pay because you simply do not get helped (are they relying on this?). So if they charge 1 million of their customers just an extra R25.00 a month, they score R***0 a month on items that people don't use/want. Values driven company - I don't think so.