Data Charge (Out of bundle)

I have been charged a ridiculous amount of money for my wife's cellphone on my account because she went out of bundle on her data. She bought 2 data bundles that month and forgot to top up (October Invoice). I cannot understand how Vodacom can charge a customer R2 per MB in this day and age. I am and have been a loyal customer for 17 years and pay what i deem a substantial amount of money monthly. This was an error by my wife but it still does not justify that Vodacom is abusing the situation with ridiculous charges.