Contract that was done wrong

In May I did an upgrade on MTN via Mundo and they delivered a wrong device in the 1st of June which I took it MTN canal walk. To date this matter hasn't been resolved and I keep on being debited every month for an amount of R13,118.90 and it is messing my credit score. I have sent MTN canal walk countless emails because every month my contract will be suspended. I have been manually paying them without fail and on the 31st of December 2022,they made the deductions again after I was told that they are handling the matter. Right now I just got back from my back to do the reversal of R13,118.90 which went through and left me penniless and I wasn't able to pay my bills. I am really not happy about all of this and it looks like no one is making an effort to resolve this issue. This happening far too long and it has to stop.