No assistants when they made a mistake

Long story in a nutshell. I canceled my topup contract with Vodacom mid June 2017. I phoned in, the operator assisted me said she will send me the quotation for the amount i have to pay. Make the payment and sign the quote. Then send back the signed paperwork along with proof of payment and id copy. I did all the above and recieved a confirmation e-mail from them that the cancellation is done. End June the debit order went off on my account. I contacted them and the apologized for the mistakes and refunded me for the debit order that was not supposed to go off seeing that the account was paid in full and closed eeeks before. Now months later i learn that according to Vodacom that i owe money on that account and was handed over. I contacted them and they went back to the emails and recorded telephone conversations from June and established that again Vodacom is in the wrong and they will credit the account and change the account from Legal to current. I phoned in numerous times speaking to over 20 people assuring me that the system is just slow but The hold up is at the credit department and that they will follow up and phone me back. That was over 2 weeks ago and i still have not heard from them. The lady fom Secunda Vodashop Jemila had been trying to assist in contacting them for me a few times but to no avail.