Angry customer

Im very angry with Telkom. I have contract with them, last year August 2022 i changed my bank details and went to the store to update new bank details. They advice need to atlist update in 3months because it new bank. Made cash payment and January went to update new bank details advice for the deductions to be on the last day of the month but till todate they are not deducting on the last they they deduct on the 15 with out my approval hense i end up reversing because i pay cash on the 3rd. I do have went to Telkom branch and also called but this issue is not resolved, every time it like they have sorted the issue. This is affecting my profile if i keep reversing. And it so frustrating now as i am not getting assisted