Over billing my account

I set a limit of a certain amount on my contract over and above the monthly minutes, which has been like that from May last year when I took out the contract. However, to my surprise, I get a statement and the account went way over that limit. Everyone that I spoken to tells me it is not Telkom mobile's fault as they are not liable for the charges that come from the usage of the sim. That is utter nonesense because I did not authorise the increase in the limit!<br> <br> I spoke to some lady by the name of Franscina with a very bad attitude who ended up hanging up on me when I ask her to check for me why this is the case.