MTN *****ing from accounts now ?

I would give no stars if possible.... I'm fuming - My debit order came off last night as normal but this month MTN decided to double debit my account, no warning ! R2289.00 instead of R1149.00. When I went to query this instore I was told after a lengthy phonecall to head office by my consultant that this has occurred due to a swap over to a new billing system and they won't re reimburse my money, from next month it will go back to my normal amount. Who on earth do these arrogant, thieving people think they are ? The bank can't help as MTN will just suspend my service if I return the debit, can anyone advise what to do or if you've had the same problem ? Surely they can't get away with this ?