Breach of contract

I signed up for a 24 Month Contract with Telkom Mobile for a Samsung Galaxy S5 in October 2014 for R399 per Month and these were the benefits that I signed up for. 100 All network minutes per month for 24 months, 1024MB All network Data per month for 24 Months, an additional 150MB all network Data per month for 24 Months, Unlimited Telkom Mobile to Telkom Mobile calls for the 1st 12 Months, 10240MB wifi per month for 24 Months and Unlimited data on Telkom network until 31 March 2015. Since I signed up, I have been receiving all that. Now after the 31st March 2015 when the unlimited data promotion came to an end, that is what I signed up for. Now they only give me 150MB all network Data and not the 1024MB All network Data that I was suppose to receive with the other services. I signed up for this contract knowing and understanding that after the Unlimited data promotion ends, I will still receive 1024MB All network data and an additional 150MB all network data for the remainder of my contract. This a pure breach of contract, so disappointed on TELKOM