Vodacom - automatic purchase of data

Some months ago I raised an issue on Hello Peter with Vodacom, which took some time (months) to resolve with Vodacom. When one's data gets low, they send an sms stating the amount of data left, and that when it runs out they will automatically purchase more data. It took quite a long time for them to stop this, however, I still get notifications from them stating low data and that there will be an auto purchase, but it seems that they don't bill me or add more data. If only they could stop the message as well.