Breach of Contract and no response

I had a 24 Months contract that expired and was informed it will be renewed month to month. I learned that Vodacom altered the term of this contract by reducing the data allocation without any notification to me , I queried this on the 4th March 2016 and was assured that the data as agreed is available and not visible to me by call centre agent ( I take it calls are recorded and the recording can be retrieved) I wanted to ensure that the invoice will be corrected and called again on the 5th of March 2016 and lady informed me that the issue is not yet rectified and send me a reference number-*** with assurance that I will be contacted within 48 hours. Today the 18th April I am told that the status is in progress .Worse still I was transferred to the so called \customer 3D and kept on line for over 35 minutes without any assistance. I received an invoice and was charged data and paid for the 1Gig which I never received. To day I spoke to gentleman called Lazi who assured me someone will come back to me. I paid thousands of Rands and frustrated by this poor service from Vodacom. PLEASE HELP"