International roaming loaded without my permission

I did an upgrade of my MTN contract. I requested the contract to be exactly the same as my previous one. The agent ensured me that all is the same. I did no get a copy of the contract only a "Customer pick-up document". My bill came to R15000. I stopped the debit order and returned it. Only to find out International roaming was loaded on my account without my knowledge or signature. Calls to the value of R12000? I have been requesting proof from MTN that I in actual fact did request International roaming I get told "here is a reference nr wait 7 working days for an answer" after 7 working days I phone again and get told the same story. My account is now handed to the legal department my cell nr has been given to someone else in the meantime. That poor lady is now also being held liable for my bill as the attorneys have her cell nr as the nr in question and my bill????? I need some help here please.