Billing disaster by unprofetional telkom mobil service provider

i took a contract with telkom and i was suppose to use my number as a the simcard contract but they never did that, now they were quite. they just came from nowhere now wana debit my bank account for the same contract they were quite about for months and now i owe R475 because they decided that i need to use my ex number that was registered to me as the contract. last time i reserved the R475 because i was not aware it was then debiting my account now its triple debit plus the charge for reversing my debit. its totally unfair what they are doing to me. i never refused to pay instead of them communicating with me about the contract and i explain my side to the they do as they please on my account and contract.