******* Debit Order

If I could give them a zero, I would. MTN debited my bank account ********ly after I paid my account via an EFT payment & now they are refusing to refund me or cancel the ******* debit order. In order for me to get the ******* debit order removed, I have to miss 2 to 3 payments. How insane is this? Because this will damage my credit score, something that I've worked very hard to rebuild.