Can't stand by there product

I have a my 2GB @ R149 a mouth open line. I have put an call limit on it for more then 4 months no and each time my call limit have block it. To day was a amount of more then R1000 over spend on my number now. I call this morning and was told that vodacom doesn't stand behind there products. Firstly i have put a limit on to my account so that i can prevent this from happening and i have checked my balance frequently and still it shows that i do have data available. I called this morning amd was told that the balance check and the call limited isn't guarantee. To me i take it as miss leading and that is *****. I want to know if vodacom can't even stand behind there products how can i as customers can believe they vodacom can guarantee there services.