Inability to help customers

Yesterday I get a courtesy sms from Mtn telling me I'm 90% through my credit limit. I go into my account to see data usage is at R3133. Never ever have my account been more than R500. I phoned 808 and got told sorry for you we have policies in place and cannot help you until the 11th. I cannot believe that a company the size of Mtn cannot help on unbilled balanes. Or maybe it's because of the size of the company that they could not give a hoot about their customers. I've been with Mtn for 14 years but I think our paths will split when my contract is up. I'm gatvol of companies that could not care less about their clients