Absurd Data charges

I received my march billing invoice for data charges of R3695 on my data contract. Upon checking my itemised billing I found that MTN are charging me for data being used since December 2014 - total data around 32GB. I logged query *** with MTN SP on 10 March 2015 and requested that I be contacted that this issue can be resolved as I am not in agreement with the billing. Until now I have not received any feedback from MTN - typically MTN - their customer service is non existent - best of all they have just closed my query - no feedback to me or informing what is going on. I logged another query on 31 March for the same billing problem. I expect that I will not received any feedback on this again and MTN will just suspend my services. I have already paid the normal monthly amount for my data and voice contract but I refuse to pay for the data usage they claim I have used. Hopefully someone from MTN will respond to this - but I'm not holding thumbs.