Debiting my bank account despite query

I have had the unfortunate situation of receiving a debit from Autopage, 6 times my standard monthly billing. Not only was there no warning from the service provider, but i also had a soft block that did not work, irrespective of them billing me every month for the service. On noticing the high amount being debited from my account and checking my online service, i found out that the additional amount was for data usage. I reversed the payment and sent a query to the Autopage Call Centre. In my message I asked that they send me proof of usage. To date this has not happened. Their response was to block my SIM, carry on billing every month and send me updated accounts. After multiple messages and calls to their call centre, which were closed with no further input i gave up and just let them debit my account for around R11K in order to close the matter and be rid of them. To date i still do not have any formal response. It seems to me like the call centre works on targets related to out standing jobs so they are not interested in actually helping people. I have just found out that they still billing me despite having sent them a letter terminating the contract. Obviously i am not alone