Inefficient customer service

My mom changed to the R599 uncapped Telkom package in December 2017. In March 2018 we noticed on her account that she was still paying the R99 a month for her previous 20GB package as well as she had been charged R1999 for the free modem that came with the new deal. We phoned and got given two reference numbers (one for the 20GB and one for the R1999). Within a few days they credited her account for the R1999. It is now November and she is still being charged for the R99 a month!! I went in to the Bluff branch on Tuesday 6th November 2018 and logged another query. The gentleman said we would receive an sms within 48hours with a new reference number. We have yet to receive the sms. Shocking service. We will definitely be cancelling the service once the 2 years is up! Please can someone tell us how to get this R99 a month stopped and to be credited for what she has been paying!!