Unauthorised Content/SMS Billing

Mtn has started again by allowing content charges to be billed without my/the customers permission, i had this problem about 4 years ago, which we sorted out, but "un-authorised content/sms charges" are back with a vengeance!!! Sneaky, a week apart, almost to the hour, from a totally unknown number ( 6666) , how do they still allow this in this day and age???????????? Unacceptable!! now we, the customer has to fight for the crediting of account!!