Reverse my contract MTN, you are a *****

I am desperate. A Mondo representative phoned me to do an upgrade for my MTN contract via the phone, once the upgrade was through, I phoned to hear why I was being debited so much and they said it was because it was an early upgrade, an upgrade that I didn’t request! I then asked Mondo to please reverse the upgrade and instead they cancelled my contract! MTN debited me R9000+ because I cancelled my contract on early termination, I NEVER even signed a form to cancel, it was all just done on my behalf without my knowledge. MTN Bloemfontein told me to reverse the debit order and now because the status of this upgrade is still pending, my credit score is blemished…. I phone on a daily basis and MTN sends me to Mondo and Mondo sends me to MTN. According to MTN they can’t reverse the upgrade because I owe R13000? Mondo won’t release the reversal because they say MTN must do that. Seriously MTN? Is everyone incompetant?