Incorrect billing of pre-paid airtime

I recently moved across to Telkom mobile on a pre-paid package and was noticing that my all network talk minutes were being depleted rather quickly. Part of Telkom Mobile's pre-paid deals is that you get FREE Telkom to Telkom and fixed land line minutes. However after having made two Telkom fixed line calls, I checked and noticed thatTelkom was billing me from my all network minutes bundle which I purchased? I called Telkom to query this with them and they confirmed that I was being incorrectly billed. I was given this case number ********** 4 but have not heard anything further from Telkom. One shouldn't have to check every call against what you are being charged by the service provider and you should be able to have confidence that you are not being ****** of your airtime. This is very concerning and disappointing for a consumer, cause who can you trust in this day and age anymore???