In IT system issues will always occur and irrespective of how much you test there will always be a slim chance of human error. There simply is no flawless and error free system and it boils down to how the company deals with the issue afterwards. From personal experience I must say that CoJ is probably the most disgraceful example there can be when it comes to issues like this - instead of taking responsibility pursuing a witch-hunt and opening a criminal case will very soon backfire.
Kudo's to CellC for fixing it so quickly.
On a side note: If it were not for users like cavedog, pointing those issues out, companies and their customers would be exposed to much worse than "just" reputational damage. For all you know, hackers could have mined that information for almost a year.
TBH - POPI does not excite me at all, as it waives any responsibility and accountability of any government organisation. So what is the point if a CellC, Vodacom or Afrihost gets fined R10m for such a violation. Guess what? The money will disappear somewhere within the government. If POPI or ECT was used to improve internet services, the quality of online businesses and internet connectivity as a whole, I would have no problem being exposed to fines.