WHY DOES TELKOM PARTNER WITH SELLDIRECT

I had an 8TA contract of data connection paying R199.00 with Telkom 8TA for 24months wit an excellent service and was very happy. When the contract expired I continued on a month to month paying R199.00 and enjoying the data with easy. However my problem started when Selldirect contacted me on behalf of Telkom and promised heaven and earth. Now I am a miserable client with no access and the promise of a more expensive contract with no access to customer service, no telephone answering but phones ringing and ringing. My issue is why did Telkom give my contact details to Selldirect without my approval. Selldirect has delivered a modem at my place which they said it would cost R199.00 per month. Thats was fine as we agreed to that. But on the 2 March 2015 I got an invoice from Telkom saying I will be paying R279.83 per month. This is unacceptable as the agreement was for R199.00 and not R279.83. I have already paid for February 2015 on the 28 February 2015 and I will not honour the payment of R279.83 on the 31 March 2015 as I dont agree with that invoice. My reference to telkom is ***4. Please investigate.