Unknown bill

Vodacom is a ****, I have been paying for an airtime advance that was included in my bill without my knowledge and o asked them to cancel the allowance but it still appears on my statement this is because my contract is about to end so they just adding money for no reason and they cannot even explain how did it amount to R515 because when I add all the extra money that I am paying it amounts that amount so. This is so wrong and they cannot even give me answers they promise to call and never get back to you.