Vodacom Does it Again

I am having endless problems with Vodacom and my account - A while ago the same thing happen where my data bundle dipletede and i was using data out of a bundle. I was then advised to set a limit on my contract so that my final amount does not exceed R650 as I have set a limit on my cellphone. The limit seemed to be working well for these few months but now all of a sudden my bill R1176 - how is this possible as I was not informed that my bill has exceeded the amount of R650. I was told by Vodacom that since a limit is in place, my account will never exceed R650 unless I call in an increase it and if my account goes to R650 it will be soft locked. I am very frustrated as I do not have the money to pay this amount of R1176. Why do you have limits set on your number if it does not work correctly. I had no indication that I was over my limit and now I am liable. This is a *******. Vodacom needs to get there facts straight before advising their customers about limits to prevent you account from reaching high amounts as it is not true. This makes me feel like leaving Vodacom as they should not mislead their customers!