Cancellation impossible

I am trying to cancel a data contract, I have made 10 calls to Vodacom to have it cancelled and on 4 occasions I was informed that it was in fact cancelled, yet I still pay for the contract. The cancellation had to be processed by 31 July 2020 and I just received the second invoice after cancellation. I even noted the cancellation to a upgrades consultant that phoned me recently, the Vodacom employee became very rude as she said it is not her department, so they have the audacity to bother me to upgrade the line but when I request assistance with the cancellation they do not want to help, pathetic service! It is a pity that there is not enough competition in our country for Vodacom to get a decent hiding that is why they do as they please.