Incorrect billing

Telkom billing is just not willing to action my case. I took a 24 month contract with Telkom. The device is now fully paid and investigation was done, outcome relieved that the device was paid for 23 of 24 . Last invoice was raised and cleared on the 25 Sep 2019 to make up the 24th Month. Telkom still continues to charge for the device even though its fully paid. Sept invoice includes the device fee. basically Telkom will continue charging for the device fee until the 22 Dec which is deemed to be their activation dates dispute the fact that the device is fully paid.