Pathetic service - Incorrect billing that cannot be resolved

I have upgraded my contract with MTN in March 2022. I took a contract with a premium of R839. Sometime in April I got a debit of R2700. I called MTN and they said it was a mistake and it will be rectified. I again got debited another R2500 plus in May and I called MTN again and they said the same story and finally refunded me. 3 months down the line I realized my services were cut off. I called they said they will fix it. My debit kept on going through and I was over charged. Of late the debit amount was slightly lower and today my services are cut off again and MTN says I owe them R13 000 plus. These amounts don’t reflect on my MTN App. Now my services are deactivated I am holding a phone which I am paying for and Can't use the services. I got even frustrated more by their useless consultant who said I should go to the branch where I took my contract and ask them to sort my issue. How is that so because the billing is done by their head office. MTN can you please cancel that bill and activate my services. I DO NOT OWE YOU MTN!