***** on my mtn contract

I upgraded my contract with MTN a few months ago and at first the agent said that the last amount a pay for the contract would be in the month that I upgraded. Then the new monthly debit order would go off afterwards, ever since I've been getting debited R200 or more above my contract price, only to find there is a number I don't know that is linked to my profile.. I AM ESSENTIALLY PAYING FOR SOMEONE ELSE'S DATA! when I try to call mtn there is no option to speak to an agent.. This is ***** and I need answers.. As well as a refund at that!