Charging for Gigs that is not used

Telkom has the worst service I have ever seen , We received a bill for R500 stating that we have used 12 BG in one day on the 10/11/2017. Telkom can not give me any detailed billing on what this supposed 12GB is used on so I have to just accept my fate and pay.. good for nothing!! Secondly there is supposed to be a cap on this so called rooter of 5GB. So how do I use 12GB????!!! Service is ********** !! Called multiple times and Telkom still cant give me the answers I request!! Can someone please for the life of me sort this out!. Wouldn't ever recommend Telkom to anybody!