Add-on internet bundles, internet usage which cannot be explained

I signed a contract in May 2016 with Telkom; this included a capped amount of R50.00 (Fifty rand). From the inception of the contract I have been incorrectly billed. I have been billed for internet bundles and extra internet usage which is not part of my contract and which I did not sign up for. I have also been billed for calls over and above the capped amount. I did not take out a contract for extra data, not verbally or in writing. The contract I signed was for R539.00 (five hundred and thirty nine rand) a month. At no time whatsoever, have I requested data or changed my limit on my contract. I would like to be reimbursed for amounts that were deducted from me in this regard. I have not been furnished with any records where I have agreed to change the terms of my contract.