Happens every few months to me as well. Spent 90 minutes on the phone with them last month going from person to person none of whom seem to know their own product or capable of understanding that x amount of data was downloaded between 12 and 7 am but has been taken off my cap and not the night data. Eventually told to send an email, which I did - no response to that.
So now I also have an Axxess account and will cancel Telkom when the contract allows.