MTN and MoNDO

I did an online upgrade of my MTN cellphone contract using MONDO, in December 2021. I received the phone via courier but it was the wrong phone as per the contract deal. I returned the phone via courier the next day, asking for the deal to be cancelled or for the phone to be replaced with the correct phone. At this stage it has been established that the returned phone was never received/booked back into stock by the warehouse and thus the phone cannot be replaced and the contract cannot be cancelled because their records show I have the upgraded phone in my possession. I have been calling biweekly/monthly to get this deal either cancelled or to be sent a new phone, but with absolute no luck and no progress being made to resolve this matter and in the meantime I am paying for this new phone and new contract, which I don’t have .