Billing on my vodacom contract

I have been sending emails to vodacom for about 2 weeks now. I have received a refund but not for the amount that was debited from my bank account. I have sent a email asking where the balance of the money has gone but no reply. I am not happy with this and nothing is been done about it. I told them that the sim card is not even in a tablet or a cellphone but i'm getting billed for data.. I need this to be sorted out and i would like the rest of the money paid back to my account. I have always paid around R500.00 per month and i was debited for R 12100.00 and which i only back around R 9200.00 so where is the rest gone? Very disappointed in the way Vodacom has handle this situation.....