Extra costs billed to me without explanation

I signed for an MTN My Choice 100 Contract in August 2014 costing R379 per month. I have been billed the following amounts since this contract became effective: R775.46, R494.87, R486.43, R501.43 and R468.49. Altech Autopage accounts cannot tell me why I am being billed for extras I haven't incurred and last month I paid R100 less than the bill stated and have since had my service suspended.<br> How can it be that noone can tell me why this bill is in excess of the amount I was quoted when I signed for this contract? Each month after receiving my bill I sit on the phone for over an hour trying to resolve this issue and I am told a query is being lodged, I am given a reference number and noone gives me any feedback? I have consumer rights and I demand that this matter is given priority asap