Overcharged monthly contract fee

I have had this contract since 14/1/2014. My monthly subscription is R269.00. This includes R200.00 free airtime, 200 MB Data + 25 Free Sms`s. I have been charged R269.00 every month , since the beginning of my contract until February 2015. On 25/02/2015 I was charged R493,77 and on 25/03/2015 I will be charged R464,05.<br> After numerous calls to the billing department I have not received a satisfactory answer to my problem. It seems to me the R200 free air time I am entitled to has fallen away after one year. <br> I have also requested an itemised statement, reflecting the usage of my R200 free airtime, which has not been supp**** to me.<br> I would like to get all my statements for the past year on this account.<br> I find the call centre incapable of solving my problem.