Over charged for cellphone bill

I received my statements every month since Dec 2014 and notice that ive been billed to much. I logged a case and i was told that the amount is what I should pay. On the 7th of May 2015 I got through to a consultant who confirmed that Im being over charged. I immidiatly logged a case with the call centre. It is the 28th of May already and no one has ever given me feedback regarding this matter even after numerous calls being made to the call centre from my side. A month and a half ago they even had the oddasity to lock my account due to none payment as I refused to pay R338. Whereby my contract is R226. Can you please help me get this right as I feel this is unfair towards me as a loyal client.