Charged for a device in Vodacom's possession.

I was due for an upgrade in September 2020 however the device provided was faulty. I logged for a return and the device was collected by RAM Couriers on behalf of Vodacom on 9 September 20. Vodacom has continued to bill me for this phone whilst it is in their possession. I have called their after sales number almost everyday so that I can apply for a new device. I was told I cannot do that as their back office has not logged the return back into Vodacom systems for a whole month, the phone still shows as delivered to me. I have provided them with a collection number from RAM Couriers & they have advised me that the device was delivered at their Midrand Warehouse however Vodacom has not ensured that this device is loaded on their system so that I can cancel the upgrade.