Poor service/billing errors

I have had my R99 contract with Cell C which is a Data bundle of 2GB monthly for up to 5 years now. In May 2015 and June 2015 I was billed with an amount of R1958.63 which I disputed and no one was prepared to listen or try and establish what caused such a huge bill. The excuse was that my account was uncapped which is surprising, because this has never happened in 5 years. I paid the R1958.63 on the 28/08/2015 following threats of legal action. I paid R99 via EFT on 30/09/2015 for October 2015 after arranging that the debit order be cancelled, however to my surprise I was debited with R156 on the 02/10/2015.I received an invoice of R168.99 to be debited on 01/12/2015.No one can explain this at your outlets and contact centre As I understand my contract is R99 monthly for data of 2GB monthly. Where does this new billing mess come from Please assist in sorting out this mess. According to my records there is a R99 that has been overpaid to Cell C(dated 30/09/2015). I want to cancel this contract.<br> on the 29/11/2015 I received a call from Nomsa Sithole who advised that I will get a call from within 48 hours however to date no one has called me nor respond to my email enquiry/complaint