Customers Liable for Telkom Blunders

I phoned in to add a reoccurring 2GB data bundle to one of my cellphones. The call center lady made a mistake and instead loaded 100MB (which will obviously not last very long). She also told me that she is unable to fix it and needed to log a call. I was told this will take 72 hours to fix.

5 days later(today) I phoned in to ask about the progress. The call center agent told me sorry, but you have not reached the turnaround time yet. I then responded by telling her that it has been over 72 hours. She then told me that 72 hours means 9 working days.

I asked her if I will be held liable for the cost if we go over as this is a mistake that Telkom made and she said yes. Now if somebody can please explain why a customer has to pay for mess ups made by Telkom? This is totally unacceptable. I asked for a 2GB package and surely if I go over the 100MB data but not over 2GB, how can I still be left liable for it if Telkom did not give me what I asked for and on top of that also messed the system up so that it will take 9 days to rectify?