Change of contract

Called in to cancel my contract on 31/12/2021 spoke to a retension agent Luanda and downgraded the contract for now not to lose the number. Confirmed twice with the qgent that they are sure will not be paying more than the amount agreed. And this after innitiating the cancelation online before. With still success, went on to pay end of January again as I thought it pays a month in qrrears. Still getting billed for the same contract and I refuse to pay any costs to the old contract. Consensus was reached in December and Vodacom is not performing as agreed. Seems like a letter of demand is required and claiming damages to ensure someone do their job.