Vodacom's non-existent customer care

A few years ago, I bought a phone for my domestic helper. The phone was ******, however, a year or so later and I cancelled the SIM card (or so I thought!). At the beginning of the year, I received an email from Vodacom, stating that my "application" for an upgrade had been approved and that the iPhone and Apple watch I apparently ordered would be delivered shortly (to an address unknown to me). I was shocked to learn that someone had bought it in my name using the other SIM card! I managed to stop the "upgrade" (after days of struggling), but that wasn't the end of it. Thousands of rands' worth of data are being purchased on that number! I visited a Vodacom store (Brooklyn) approximately six times, contacted and emailed the ***** department, filled in loads of forms and spent hours on the phone with consultants, attempting to cancel that SIM card. However, once again, the most recent invoice includes data bought on it! I don't understand - how difficult can it be to cancel a SIM card??????!!!!! This, after I received an email from Vodacom earlier this week, stating that the issue had been resolved and the invoice credited. What else am I supposed to do????!!!!