Incorrect billing

I took an "UNCAPPED" wifi 10mbps contract with Telkom via the phone and the amount given to be was @R700 and I was told is cheaper because I stay in one of the community that had a deal with Telkom and I accepted the offer. The 1st 2 months the invoice amount what I agreed on. The 3rd invoice came with ridiculous amount which was more with about R300.

I logged the call with them and the call was closed without getting any feedback. The bill for each and every month keeps on increasing and now Telkom is billing me @R1000 per month. I tried phoning them but Im not getting any luck. I phone their accounts department and they told me to phone the sales department and when I phone sales department they say I must phone finance department. It has been more than 4 months trying to resolve the issue and I'm not getting luck.

Can someone from Telkom assist me in resolving this mess.