Debting accounting without authorisation

On the 31 Jan my account was debit and additional R89 not stipulated to my MTN contract on investigation with MTN, Victoria Technologies put this amount onto my account. A lady by a name of Portia from Victoria Technologies (contact no. ***) contacted me later that day and told me it would be reversed into my account this was 2and a Half weeks ago, I now have received my MTN statement and the same practice is taking place when I was specific I did NOT register for such a service. Victoria Technologies also confirmed that my number is not on there database. So this in turn shows the are *******ly acquiring funds from my account and have the intension on doing so again this month. The amount maybe small but its the principle and how many other people are they ********. MTN is of no help either I have called and complained numerous times to the MTN and still nothing is being done both sides. Please can you help as I don't know what more to do to stop this ******* in my book.