Vodacom just deduct money from my bank account

I'm a loyal supporter of Vodacom but at this moment I'm beyond angry. I received a call from Vodashop Ceres about a month ago to say that my account was debited from someone else's bank account. After a long wait I was called to update my banking details, which they did. Then on Monday Vodashop Ceres phoned me again to say that the amount will go off on Monday. I'm fuming because it's a month and no one from Vodacom called me to make payment arrangements and/or just a call to say how this whole story happened. Now I have limited funds and they need to pay the money back. Who gives Vodacom the right to deduct money off my account other that my monthly account. Poor service and unprofessional.