Upgrade gone wrong

I got a call from Vodacom telling me my contract is due for an upgrade. I decided to upgrade and get an iPad Air. Upon arrival of the device I received an iPhone 15 instead of an iPad Air. I immediately called customer care and asked to return the device and to cancel the whole contract. They fetched the device. 3 months later I am still being billed for a device I do not have and did not use. I am still being billed for a contract that I asked to be cancelled. So basically they did not cancel the contract. When I call the billing call centre I am told that they’ll make a dispute and it’s under investigation. I’ve been told this for the last 3 months but still being billed and have received no response or feedback from the dispute made or from the “investigation”. What is there to even investigate , I got the wrong device and I don’t want the contact anymore it’s as simple as that. I refused to pay. Now my SIM card has been suspended. This whole situation is due to their own negligence and incompetence why must I pay for a phone I did not ask for and which has been returned to them. So disappointing and frustrating. Such nonsense from Vodacom