Shocked - R4950 Bill for R800 contract

I've received a R4950 Bill for September after I tried my best to be conservative and not use out of Bundle Data. Out of Usage Data amount was R3200.00. I was given a warning by my company for previous high bills. Maximum was R1900 for a R800 p/m contract. So the last bill is gonna be a big problem for me. Vodacom not really helpful to reveal detailed information. I've been a customer for more than 10 years and my bill has never been that high. Now I feel like I'm being targeted with *****elent billing. And just ironic that I received the highest bill ever in the month I tried to be really conservative. Not sure what to do.