Limit on contract however data overcharged

I have a limit on my account of R300 & my billing has not exceeded R600 since upgrading my contract.To my knowledge when you reach your limit,the service get suspended immediately,however when I used the internet on Sunday, 6 September 2015,Vodacom has simply continued to bill my account even after reaching the limit. My phone was suspended on Monday & when calling customer service to increase my limit to enable me to use my phone,I discovered that my bill was R2 600.I contacted them again to query the billing and was told by Zakhele (incident ***) that when clients use the internet,Vodacom doesn't want to interrupt clients. A few days later, Candice Petersen contacted me and said that Vodacom doesn't update information in real time, hence the billing, contradicting what Zakhele said. Then only was the terms & conditions explained to me & an e-mail sent to me to sign. Candice also told me that as a goodwill gesture they will convert the data used & charge me as if it was bundled data. The next mail I received was a bill of R2277 without a breakdown of the calculation which I'm not prepared to pay. I'm a very unhappy client who has been loyal. (e-mail reference: S3-8GX3L-LQQP)