Telkom billing mess

I have a Telkom wifi contract that i got in November 2016. I was initially on the 5Gb plan for which i paid R199 per month. I later upgraded to a 10Gb plan for which I've been paying R299. On the 30th March Telkom debited me R699 and when i checked my invoice there was a R500 charge which i have queried to no avail. On the account summary of my invoice it is listed as "Account subscription and once 0ff charges" in the detailed invoice section the R500 is listed as "Data bonus bundle awarded." When i took this contract I specifically asked that it should be capped such that if i run out of data my Internet connection should be disconnected and i would have to top up if i want to continue browsing. I have been doing so. I have logged 3 queries with Telkom but issue is still not resolved and neither did i receive a refund. This morning i received my invoice and again that R500 charge is there. This is unacceptable. And none of the Telkom consultants i spoke to have been able to explain this extra charge. I am appalled by this kind of service from Telkom. Why would my account suddenly incur an extra charge of R500 which no one can explain. I need my refund. And with the latest invoice they want to debit me R717. And on top of that the consultant told me they charge R800 to cancel the contract. I cannot continue to have money that i desperately need just debited from my bank account willy nilly. This is unacceptable.