Vodacom deleted banking details before the last debit order can go through and therefore I am blacklisted by credit bureau

I had a 24 months data contract with vodacom which was suppose to end Dec or Jan 2017. When the last debit order was in December, I assumed the contract has ended. When I try to apply credit card from Discovery and other financial institutions, they told me there is a problem with my credit record. I obtained a report from TransUnion and everything is fine except a default or non payment under Vodacom. I called Vodacom and the consultant said the last debit order was suppose to go off in January but they deleted my banking details on their side so the payment couldn't be processed. I have called them several times but I am not sure how to make the payment and how Vodacom to go to the credit bureau and fix my credit score. The debit order is small amount but the error from Vodacom caused such inconvenience for me. I cannot apply for new credit card or store card, I cannot even increase my credit limit due to the failed debit order.