Billed for BIS on a Samsung Phone

I have been paying R558 for my accounts since I have three contracts. I am told today that not only am I paying BIS on a Samsung phone for which I requested that BIS be cancelled the day I upgraded for the phone in April, I am now being told that Vodacom has remembered that in August 2014, while I was out of the country, I asked to have Dual Billing activated on my account but they are only billing me now. <br> I want this bill of R668 reversed back to the previous months bills. I was told previously by accounts that they have 7working days to change the bill, now Kgomotso tells me because its previous months bill, they can't change it? Really? more than 7working days before my debit order date?