DATA *******!!!

I have a Smart L package with a limit of R350. On the morning of the 15th I wake up and my line is locked. I call customer care and I froze when the consultant told me my data bill is R5075!!!! overnight. 1stly - How does this happen if I have a limit on my phone???is that not the purpose of the limit????to make sure that I don't go to levels that I cannot afford? Secondly - I have a high usage notification on my phone, WHY WAS I NOT NOTIFIED??? in a rush I asked the consultant to unlock my phone by increasing my limit. Today (19th) I get an sms notifying me of high data usage 3 days later!!!!! To my surprise Vodacom does not limit the data it only limits calls! only after they are happy to run up a bill of what ever amount does the service cut if an applications is running. I mean what nonsense is that!!! I have been a client for so many years and every month my bill is around R2000 and this is how Vodacom repays my loyalty! I might as well change service providers because this absurd!!!!! and when I call customer care querying about my account I get the most pathetic service ever!!!! Un-Believable !!!!!