CREDIT CARD DEBIT ORDER NOT DEDUCTED

I got a Laptop contract from Vodacom on 29 March and signed a debit order for them to deduct the money from my credit card as my other Vodacom account also goes off the credit card. I was told to pay R105 once off fee, which I did. This whole month I've been getting sms's from Vodacom stating that the account is in arrears. I phoned for a statement balance via the automated service and my account was in order. Then I phoned and they told me that it was the laptop contract that was in arrears. HOW???? when I signed a debit order? I work on a farm and we don't have cellphone reception and their accounts department refuses to contact me on my land line to discuss the payment. I don't see why I should pay for the telephone call as I'm not the one that *****ed up and you just end up holding on forever listening to a computer. I visited the branch where I took out the account only to be told that they can't help me and that I should call the call centre. When telling the sales lady that I'm going to bring the computer back and shove it where the son doesn't shine she told me to do what I want. I WANT TO CANCEL THIS ACCOUNT!!!!