Incorrect charges for internet

in August 2015 I app**** for a land line and basic internet for R399.00 as told by the lady at telesales. My line and all got installed in September and never received any bill by the middle of November. I then called the customer care line and one was e-mailed and I then discovered I was being charged R899.00 for uncapped internet, which I did not agree to. The lady then lodges a dispute and told me it takes 10 days. December statement the same thing happened and I once again called and a dispute was once again lodged. January statement came and the exact same thing again, so I went to Telkom Tygervalley and was told by the sales lady it has nothing to do with them, Very disgusted and frustrated I left. I then contacted them via facebook, 5 messages was sent with the same reply \we apologise and mark your case as high priority\". I have now received letters of demand and been told I will be black listed if I do not pay. I am in the process of buying a new home and do not really need this in my life. I have now decided to go pay this amount and if I do not get a response/refund from Telkom within 14 days I will have to send my own lawyers letter. They have the tape recordings surely"