Unauthorised deduction

Someone managed to deduct R9,200 from my MTN account! Why do I have to prove my innocence by schlepping to the police station to do an affidavit? Why can't they trace the documents that someone must have processed on THEIR SIDE. After all one is required to provide proof of residence, ID & 3 months documents! So where are these documents that authorises this HUGE deduction from my account. Absolutely appalling!